Refitter

Refitter is a tool for generating a C# REST API Client using the Refit library. Refitter can generate the Refit interface and contracts from OpenAPI specifications. Refitter could format the generated Refit interface to be managed by Apizr (v6+) and generate some registration helpers too.

Refitter comes in 2 forms:

• A .NET CLI Tool distributed via nuget.org that outputs a single C# file on disk
• A C# Source Generator via the Refitter.SourceGenerator package that generates code on compile time based on a .refitter within the project directory.

CLI Tool

Installation:

The tool is packaged as a .NET Tool and is published to nuget.org. You can install the latest version of this tool like this:

dotnet tool install --global Refitter

Usage:

$ refitter --help

USAGE:
    refitter [URL or input file] [OPTIONS]

EXAMPLES:
    refitter ./openapi.json
    refitter https://petstore3.swagger.io/api/v3/openapi.yaml
    refitter ./openapi.json --settings-file ./openapi.refitter --output ./GeneratedCode.cs
    refitter ./openapi.json --namespace "Your.Namespace.Of.Choice.GeneratedCode" --output ./GeneratedCode.cs
    refitter ./openapi.json --namespace "Your.Namespace.Of.Choice.GeneratedCode" --internal
    refitter ./openapi.json --output ./IGeneratedCode.cs --interface-only
    refitter ./openapi.json --output ./GeneratedContracts.cs --contract-only
    refitter ./openapi.json --use-api-response
    refitter ./openapi.json --cancellation-tokens
    refitter ./openapi.json --no-operation-headers
    refitter ./openapi.json --no-accept-headers
    refitter ./openapi.json --use-iso-date-format
    refitter ./openapi.json --additional-namespace "Your.Additional.Namespace" --additional-namespace "Your.Other.Additional.Namespace"
    refitter ./openapi.json --multiple-interfaces ByEndpoint
    refitter ./openapi.json --tag Pet --tag Store --tag User
    refitter ./openapi.json --match-path '^/pet/.*'
    refitter ./openapi.json --trim-unused-schema
    refitter ./openapi.json --trim-unused-schema  --keep-schema '^Model$' --keep-schema '^Person.+'
    refitter ./openapi.json --no-deprecated-operations
    refitter ./openapi.json --operation-name-template '{operationName}Async'
    refitter ./openapi.json --optional-nullable-parameters
    refitter ./openapi.json --use-polymorphic-serialization

ARGUMENTS:
    [URL or input file]    URL or file path to OpenAPI Specification file

OPTIONS:
                                                DEFAULT                                                                                                                                                    
    -h, --help                                                   Prints help information                                                                                                                   
    -v, --version                                                Prints version information                                                                                                                
    -s, --settings-file                                          Path to .refitter settings file. Specifying this will ignore all other settings (except for --output)                                     
    -n, --namespace                             GeneratedCode    Default namespace to use for generated types                                                                                              
        --contracts-namespace                                    Default namespace to use for generated contracts                                                                                          
    -o, --output                                Output.cs        Path to Output file or folder (if multiple files are generated)                                                                           
        --contracts-output                                       Output path for generated contracts. Enabling this automatically enables generating multiple files                                        
        --no-auto-generated-header                               Don't add <auto-generated> header to output file                                                                                          
        --no-accept-headers                                      Don't add <Accept> header to output file                                                                                                  
        --interface-only                                         Don't generate contract types                                                                                                             
        --contract-only                                          Don't generate clients                                                                                                                    
        --use-api-response                                       Return Task<IApiResponse<T>> instead of Task<T>                                                                                           
        --use-observable-response                                Return IObservable instead of Task                                                                                                        
        --internal                                               Set the accessibility of the generated types to 'internal'                                                                                
        --cancellation-tokens                                    Use cancellation tokens                                                                                                                   
        --no-operation-headers                                   Don't generate operation headers                                                                                                          
        --no-logging                                             Don't log errors or collect telemetry                                                                                                     
        --additional-namespace                                   Add additional namespace to generated types                                                                                               
        --exclude-namespace                                      Exclude namespace on generated types                                                                                                      
        --use-iso-date-format                                    Explicitly format date query string parameters in ISO 8601 standard date format using delimiters (2023-06-15)                             
        --multiple-interfaces                                    Generate a Refit interface for each endpoint. May be one of ByEndpoint, ByTag                                                             
        --multiple-files                                         Generate multiple files instead of a single large file.                                                                                   
                                                                 The output files can be the following:                                                                                                    
                                                                 - RefitInterfaces.cs                                                                                                                      
                                                                 - DependencyInjection.cs                                                                                                                  
                                                                 - Contracts.cs                                                                                                                            
        --match-path                                             Only include Paths that match the provided regular expression. May be set multiple times                                                  
        --tag                                                    Only include Endpoints that contain this tag. May be set multiple times and result in OR'ed evaluation                                    
        --skip-validation                                        Skip validation of the OpenAPI specification                                                                                              
        --no-deprecated-operations                               Don't generate deprecated operations                                                                                                      
        --operation-name-template                                Generate operation names using pattern. When using --multiple-interfaces ByEndpoint, this is name of the Execute() method in the interface
        --optional-nullable-parameters                           Generate nullable parameters as optional parameters                                                                                       
        --trim-unused-schema                                     Removes unreferenced components schema to keep the generated output to a minimum                                                          
        --keep-schema                                            Force to keep matching schema, uses regular expressions. Use together with "--trim-unused-schema". Can be set multiple times              
        --no-banner                                              Don't show donation banner                                                                                                                
        --skip-default-additional-properties                     Set to true to skip default additional properties                                                                                         
        --operation-name-generator              Default          The NSwag IOperationNameGenerator implementation to use.                                                                                  
                                                                 May be one of:                                                                                                                            
                                                                 - Default                                                                                                                                 
                                                                 - MultipleClientsFromOperationId                                                                                                          
                                                                 - MultipleClientsFromPathSegments                                                                                                         
                                                                 - MultipleClientsFromFirstTagAndOperationId                                                                                               
                                                                 - MultipleClientsFromFirstTagAndOperationName                                                                                             
                                                                 - MultipleClientsFromFirstTagAndPathSegments                                                                                              
                                                                 - SingleClientFromOperationId                                                                                                             
                                                                 - SingleClientFromPathSegments                                                                                                            
                                                                 See https://refitter.github.io/api/Refitter.Core.OperationNameGeneratorTypes.html for more information                                    
        --immutable-records                                      Generate contracts as immutable records instead of classes                                                                                
        --use-apizr                                              Use Apizr by:                                                                                                                             
                                                                 - Adding a final IApizrRequestOptions options parameter to all generated methods                                                          
                                                                 - Providing cancellation tokens by Apizr request options instead of a dedicated parameter                                                 
                                                                 - Using method overloads instead of optional parameters                                                                                   
                                                                 See https://refitter.github.io for more information and https://www.apizr.net to get started with Apizr                                   
        --use-dynamic-querystring-parameters                     Enable wrapping multiple query parameters into a single complex one. Default is no wrapping.                                              
                                                                 See https://github.com/reactiveui/refit?tab=readme-ov-file#dynamic-querystring-parameters for more information                            
        --use-polymorphic-serialization                          Use System.Text.Json polymorphic serialization.                                                                                           
                                                                 Replaces NSwag JsonInheritanceConverter attributes with System.Text.Json JsonPolymorphicAttributes.                                       
                                                                 To have the native support of inheritance (de)serialization and fallback to base types when                                               
                                                                 payloads with (yet) unknown types are offered by newer versions of an API                                                                 
                                                                 See https://learn.microsoft.com/en-us/dotnet/standard/serialization/system-text-json/polymorphism for more information                    
        --disposable                                             Generate refit clients that implement IDisposable                                                                                         

To generate code from an OpenAPI specifications file, run the following:

$ refitter [path to OpenAPI spec file] --namespace "[Your.Namespace.Of.Choice.GeneratedCode]"

This will generate a file called Output.cs which contains the Refit interface and contract classes generated using NSwag

Source Generator

Refitter is available as a C# Source Generator that uses the Refitter.Core library for generating a REST API Client using the Refit library. Refitter can generate the Refit interface from OpenAPI specifications. Refitter could format the generated Refit interface to be managed by Apizr and generate some registration helpers too.

The Refitter source generator is a bit untraditional in a sense that it creates a folder called Generated in the same location as the .refitter file and generates files to disk under the Generated folder (can be changed with --outputFolder). The source generator output should be included in the project and committed to source control. This is done because there is no other way to trigger the Refit source generator to pickup the Refitter generated code

(Translation: I couldn't for the life of me figure how to get that to work, sorry)

Installation

The source generator is distributed as a NuGet package and should be installed to the project that will contain the generated code

dotnet add package Refitter.SourceGenerator

Usage

This source generator generates code based on any .refitter file included to the project as AdditionalFiles.

The generator can automatically detect all .refitter files inside the project that referenced the Refitter.SourceGenerator package and there is no need to include them manually as AdditionalFiles

.Refitter File format

The following is an example .refitter file

{
  "openApiPath": "/path/to/your/openAPI", // Required
  "namespace": "Org.System.Service.Api.GeneratedCode", // Optional. Default=GeneratedCode
  "contractsNamespace": "Org.System.Service.Api.GeneratedCode.Contracts", // Optional. Default=GeneratedCode
  "naming": {
    "useOpenApiTitle": false, // Optional. Default=true
    "interfaceName": "MyApiClient" // Optional. Default=ApiClient
  },
  "generateContracts": true, // Optional. Default=true
  "generateClients": true, // Optional. Default=true
  "generateXmlDocCodeComments": true, // Optional. Default=true
  "generateStatusCodeComments": true, // Optional. Default=true
  "addAutoGeneratedHeader": true, // Optional. Default=true
  "addAcceptHeaders": true, // Optional. Default=true
  "returnIApiResponse": false, // Optional. Default=false
  "responseTypeOverride": { // Optional. Default={}
    "File_Upload": "IApiResponse",
    "File_Download": "System.Net.Http.HttpContent"
  },
  "generateOperationHeaders": true, // Optional. Default=true
  "typeAccessibility": "Public", // Optional. Values=Public|Internal. Default=Public
  "useCancellationTokens": false, // Optional. Default=false
  "useIsoDateFormat": false, // Optional. Default=false
  "multipleInterfaces": "ByEndpoint", // Optional. May be one of "ByEndpoint" or "ByTag"
  "generateDeprecatedOperations": false, // Optional. Default=true
  "operationNameTemplate": "{operationName}Async", // Optional. Must contain {operationName} when multipleInterfaces != ByEndpoint
  "optionalParameters": false, // Optional. Default=false
  "outputFolder": "../CustomOutput" // Optional. Default=./Generated
  "outputFilename": "RefitInterface.cs", // Optional. Default=Output.cs for CLI tool
  "contractsOutputFolder": "../Contracts", // Optional. Default=NULL
  "generateMultipleFiles": false, // Optional. Default=false
  "additionalNamespaces": [ // Optional
    "Namespace1",
    "Namespace2"
  ],
  "includeTags": [ // Optional. OpenAPI Tag to include when generating code
    "Pet",
    "Store",
    "User"
  ],
  "includePathMatches": [ // Optional. Only include Paths that match the provided regular expression
    "^/pet/.*",
    "^/store/.*"
  ],
  "trimUnusedSchema": false, // Optional. Default=false
  "keepSchemaPatterns": [ // Optional. Force to keep matching schema, uses regular expressions. Use together with trimUnusedSchema=true
    "^Model$",
    "^Person.+"
  ],
  "generateDefaultAdditionalProperties": true, // Optional. default=true
  "operationNameGenerator": "Default", // Optional. May be one of Default, MultipleClientsFromOperationId, MultipleClientsFromPathSegments, MultipleClientsFromFirstTagAndOperationId, MultipleClientsFromFirstTagAndOperationName, MultipleClientsFromFirstTagAndPathSegments, SingleClientFromOperationId, SingleClientFromPathSegments
  "immutableRecords": false,
  "useDynamicQuerystringParameters": true, // Optional. Default=false
  "usePolymorphicSerialization": true, // Optional. Default=false
  "generateDisposableClients": true, // Optional. Default=false
  "dependencyInjectionSettings": { // Optional
    "baseUrl": "https://petstore3.swagger.io/api/v3", // Optional. Leave this blank to set the base address manually
    "httpMessageHandlers": [ // Optional
        "AuthorizationMessageHandler", 
        "TelemetryMessageHandler" 
    ],
    "usePolly": true, // DEPRECATED - Use "transientErrorHandler": "None|Polly|HttpResilience" instead
    "transientErrorHandler": "HttpResilience", // Optional. Set this to configure transient error handling with a retry policy that uses a jittered backoff. May be one of None, Polly, HttpResilience
    "maxRetryCount": 3, // Optional. Default=6
    "firstBackoffRetryInSeconds": 0.5 // Optional. Default=1.0
  },
  "apizrSettings": { // Optional
    "withRequestOptions": true, // Optional. Default=true
    "withRegistrationHelper": true, // Optional. Default=false
    "withCacheProvider": "InMemory", // Optional. Values=None|Akavache|MonkeyCache|InMemory|DistributedAsString|DistributedAsByteArray. Default=None
    "withPriority": true, // Optional. Default=false
    "withMediation": true, // Optional. Default=false
    "withOptionalMediation": true, // Optional. Default=false
    "withMappingProvider": "AutoMapper", // Optional. Values=None|AutoMapper|Mapster. Default=None
    "withFileTransfer": true // Optional. Default=false
  },
  "codeGeneratorSettings": { // Optional. Default settings are the values set in this example
    "requiredPropertiesMustBeDefined": true,
    "generateDataAnnotations": true,
    "anyType": "object",
    "dateType": "System.DateTimeOffset",
    "dateTimeType": "System.DateTimeOffset",
    "timeType": "System.TimeSpan",
    "timeSpanType": "System.TimeSpan",
    "arrayType": "System.Collections.Generic.ICollection",
    "dictionaryType": "System.Collections.Generic.IDictionary",
    "arrayInstanceType": "System.Collections.ObjectModel.Collection",
    "dictionaryInstanceType": "System.Collections.Generic.Dictionary",
    "arrayBaseType": "System.Collections.ObjectModel.Collection",
    "dictionaryBaseType": "System.Collections.Generic.Dictionary",
    "propertySetterAccessModifier": "",
    "generateImmutableArrayProperties": false,
    "generateImmutableDictionaryProperties": false,
    "handleReferences": false,
    "jsonSerializerSettingsTransformationMethod": null,
    "generateJsonMethods": false,
    "enforceFlagEnums": false,
    "inlineNamedDictionaries": false,
    "inlineNamedTuples": true,
    "inlineNamedArrays": false,
    "generateOptionalPropertiesAsNullable": false,
    "generateNullableReferenceTypes": false,
    "generateNativeRecords": false,
    "generateDefaultValues": true,
    "inlineNamedAny": false,
    "excludedTypeNames": [
      "ExcludedTypeFoo",
      "ExcludedTypeBar"
    ]
  }
}

• openApiPath - points to the OpenAPI Specifications file. This can be the path to a file stored on disk, relative to the .refitter file. This can also be a URL to a remote file that will be downloaded over HTTP/HTTPS
• namespace - the namespace used in the generated code. If not specified, this defaults to GeneratedCode
• naming.useOpenApiTitle - a boolean indicating whether the OpenApi title should be used. Default is true
• naming.interfaceName - the name of the generated interface. The generated code will automatically prefix this with I so if this set to MyApiClient then the generated interface is called IMyApiClient. Default is ApiClient
• generateContracts - a boolean indicating whether contracts should be generated. A use case for this is several API clients use the same contracts. Default is true
• generateClients: - a boolean indicating whether clients should be generated. A use case for this is to seperate clients and contracts in two generation
• generateXmlDocCodeComments - a boolean indicating whether XML doc comments should be generated. Default is true
• generateStatusCodeComments - a boolean indicating whether the XML docs for ApiException and IApiResponse contain detailed descriptions for every documented status code. Default is true
• addAutoGeneratedHeader - a boolean indicating whether XML doc comments should be generated. Default is true
• addAcceptHeaders - a boolean indicating whether to add accept headers [Headers("Accept: application/json")]. Default is true
• returnIApiResponse - a boolean indicating whether to return IApiResponse<T> objects. Default is false
• responseTypeOverride - a dictionary with operation ids (as specified in the OpenAPI document) and a particular return type to use. The types are wrapped in a task, but otherwise unmodified (so make sure to specify or import their namespaces). Default is {}
• generateOperationHeaders - a boolean indicating whether to use operation headers in the generated methods. Default is true
• typeAccessibility - the generated type accessibility. Possible values are Public and Internal. Default is Public
• useCancellationTokens - Use cancellation tokens in the generated methods. Default is false
• useIsoDateFormat - Set to true to explicitly format date query string parameters in ISO 8601 standard date format using delimiters (for example: 2023-06-15). Default is false
• multipleInterfaces - Set to ByEndpoint to generate an interface for each endpoint, or ByTag to group Endpoints by their Tag (like SwaggerUI groups them).
• outputFolder - a string describing a relative path to a desired output folder. Default is ./Generated
• outputFilename - Output filename. Default is Output.cs when used from the CLI tool, otherwise its the .refitter filename. So Petstore.refitter becomes Petstore.cs.
• additionalNamespaces - A collection of additional namespaces to include in the generated file. A use case for this is when you want to reuse contracts from a different namespace than the generated code. Default is empty
• includeTags - A collection of tags to use a filter for including endpoints that contain this tag.
• includePathMatches - A collection of regular expressions used to filter paths.
• generateDeprecatedOperations - a boolean indicating whether deprecated operations should be generated or skipped. Default is true
• operationNameTemplate - Generate operation names using pattern. This must contain the string {operationName}. An example usage of this could be {operationName}Async to suffix all method names with Async
• optionalParameters - Generate non-required parameters as nullable optional parameters
• trimUnusedSchema - Removes unreferenced components schema to keep the generated output to a minimum
• keepSchemaPatterns: A collection of regular expressions to force to keep matching schema. This is used together with trimUnusedSchema
• generateDefaultAdditionalProperties: Set to false to skip default additional properties. Default is true
• operationNameGenerator: The NSwag IOperationNameGenerator implementation to use. See https://refitter.github.io/api/Refitter.Core.OperationNameGeneratorTypes.html
• immutableRecords: Set to true to generate contracts as immutable records instead of classes. Default is false
• useDynamicQuerystringParameters: Set to true to wrap multiple query parameters into a single complex one. Default is false (no wrapping). See https://github.com/reactiveui/refit?tab=readme-ov-file#dynamic-querystring-parameters for more information.
• dependencyInjectionSettings - Setting this will generated extension methods to IServiceCollection for configuring Refit clients
  • baseUrl - Used as the HttpClient base address. Leave this blank to manually set the base URL
  • httpMessageHandlers - A collection of HttpMessageHandler that is added to the HttpClient pipeline
  • usePolly - (DEPRECATED) Set this to true to configure the HttpClient to use Polly using a retry policy with a jittered backoff
  • transientErrorHandler: Set this to configure transient error handling with a retry policy that uses a jittered backoff. See https://refitter.github.io/api/Refitter.Core.TransientErrorHandler.html
  • firstBackoffRetryInSeconds - This is the duration of the initial retry backoff. Default is 1 second
• apizrSettings - Setting this will format Refit interface to be managed by Apizr. See https://www.apizr.net for more information
  • withRequestOptions - Tells if the Refit interface methods should have a final IApizrRequestOptions options parameter
  • withRegistrationHelper - Tells if Refitter should generate Apizr registration helpers (extended with dependencyInjectionSettings set, otherwise static)
  • withCacheProvider - Set the cache provider to be used
  • withPriority - Tells if Apizr should handle request priority
  • withMediation - Tells if Apizr should handle request mediation (extended only)
  • withOptionalMediation - Tells if Apizr should handle optional request mediation (extended only)
  • withMappingProvider - Set the mapping provider to be used
  • withFileTransfer - Tells if Apizr should handle file transfer
• codeGeneratorSettings - Setting this allows customization of the NSwag generated types and contracts
  • requiredPropertiesMustBeDefined - Default is true,
  • generateDataAnnotations - Default is true,
  • anyType - Default is object,
  • dateType - Default is System.DateTimeOffset,
  • dateTimeType - Default is System.DateTimeOffset,
  • timeType - Default is System.TimeSpan,
  • timeSpanType - Default is System.TimeSpan,
  • arrayType - Default is System.Collections.Generic.ICollection,
  • dictionaryType - Default is System.Collections.Generic.IDictionary,
  • arrayInstanceType - Default is System.Collections.ObjectModel.Collection,
  • dictionaryInstanceType - Default is System.Collections.Generic.Dictionary,
  • arrayBaseType - Default is System.Collections.ObjectModel.Collection,
  • dictionaryBaseType - Default is System.Collections.Generic.Dictionary,
  • propertySetterAccessModifier - Default is ``,
  • generateImmutableArrayProperties - Default is false,
  • generateImmutableDictionaryProperties - Default is false,
  • handleReferences - Default is false,
  • jsonSerializerSettingsTransformationMethod - Default is null,
  • generateJsonMethods - Default is false,
  • enforceFlagEnums - Default is false,
  • inlineNamedDictionaries - Default is false,
  • inlineNamedTuples - Default is true,
  • inlineNamedArrays - Default is false,
  • generateOptionalPropertiesAsNullable - Default is false,
  • generateNullableReferenceTypes - Default is false,
  • generateNativeRecords - Default is false
  • generateDefaultValues - Default is true
  • inlineNamedAny - Default is false
  • excludedTypeNames - Default is empty

Using the generated code

Here's an example generated output from the Swagger Petstore example using the default settings

CLI Tool

$ refitter ./openapi.json --namespace "Your.Namespace.Of.Choice.GeneratedCode"

Source Generator **.refitter file**

{
  "openApiPath": "./openapi.json",
  "namespace": "Your.Namespace.Of.Choice.GeneratedCode"
}

Output

using Refit;
using System.Collections.Generic;
using System.Text.Json.Serialization;
using System.Threading.Tasks;

namespace Your.Namespace.Of.Choice.GeneratedCode
{
    [System.CodeDom.Compiler.GeneratedCode("Refitter", "1.0.0.0")]
    public partial interface ISwaggerPetstore
    {
        /// <summary>Update an existing pet</summary>
        /// <remarks>Update an existing pet by Id</remarks>
        /// <param name="body">Update an existent pet in the store</param>
        /// <returns>Successful operation</returns>
        /// <exception cref="ApiException">
        /// Thrown when the request returns a non-success status code:
        /// <list type="table">
        /// <listheader>
        /// <term>Status</term>
        /// <description>Description</description>
        /// </listheader>
        /// <item>
        /// <term>400</term>
        /// <description>Invalid ID supplied</description>
        /// </item>
        /// <item>
        /// <term>404</term>
        /// <description>Pet not found</description>
        /// </item>
        /// <item>
        /// <term>405</term>
        /// <description>Validation exception</description>
        /// </item>
        /// </list>
        /// </exception>
        [Headers("Accept: application/xml, application/json")]
        [Put("/pet")]
        Task<Pet> UpdatePet([Body] Pet body);

        /// <summary>Add a new pet to the store</summary>
        /// <remarks>Add a new pet to the store</remarks>
        /// <param name="body">Create a new pet in the store</param>
        /// <returns>Successful operation</returns>
        /// <exception cref="ApiException">
        /// Thrown when the request returns a non-success status code:
        /// <list type="table">
        /// <listheader>
        /// <term>Status</term>
        /// <description>Description</description>
        /// </listheader>
        /// <item>
        /// <term>405</term>
        /// <description>Invalid input</description>
        /// </item>
        /// </list>
        /// </exception>
        [Headers("Accept: application/xml, application/json")]
        [Post("/pet")]
        Task<Pet> AddPet([Body] Pet body);

        /// <summary>Finds Pets by status</summary>
        /// <remarks>Multiple status values can be provided with comma separated strings</remarks>
        /// <param name="status">Status values that need to be considered for filter</param>
        /// <returns>successful operation</returns>
        /// <exception cref="ApiException">
        /// Thrown when the request returns a non-success status code:
        /// <list type="table">
        /// <listheader>
        /// <term>Status</term>
        /// <description>Description</description>
        /// </listheader>
        /// <item>
        /// <term>400</term>
        /// <description>Invalid status value</description>
        /// </item>
        /// </list>
        /// </exception>
        [Headers("Accept: application/json")]
        [Get("/pet/findByStatus")]
        Task<ICollection<Pet>> FindPetsByStatus([Query] Status? status);

        /// <summary>Finds Pets by tags</summary>
        /// <remarks>Multiple tags can be provided with comma separated strings. Use tag1, tag2, tag3 for testing.</remarks>
        /// <param name="tags">Tags to filter by</param>
        /// <returns>successful operation</returns>
        /// <exception cref="ApiException">
        /// Thrown when the request returns a non-success status code:
        /// <list type="table">
        /// <listheader>
        /// <term>Status</term>
        /// <description>Description</description>
        /// </listheader>
        /// <item>
        /// <term>400</term>
        /// <description>Invalid tag value</description>
        /// </item>
        /// </list>
        /// </exception>
        [Headers("Accept: application/json")]
        [Get("/pet/findByTags")]
        Task<ICollection<Pet>> FindPetsByTags([Query(CollectionFormat.Multi)] IEnumerable<string> tags);

        /// <summary>Find pet by ID</summary>
        /// <remarks>Returns a single pet</remarks>
        /// <param name="petId">ID of pet to return</param>
        /// <returns>successful operation</returns>
        /// <exception cref="ApiException">
        /// Thrown when the request returns a non-success status code:
        /// <list type="table">
        /// <listheader>
        /// <term>Status</term>
        /// <description>Description</description>
        /// </listheader>
        /// <item>
        /// <term>400</term>
        /// <description>Invalid ID supplied</description>
        /// </item>
        /// <item>
        /// <term>404</term>
        /// <description>Pet not found</description>
        /// </item>
        /// </list>
        /// </exception>
        [Headers("Accept: application/xml, application/json")]
        [Get("/pet/{petId}")]
        Task<Pet> GetPetById(long petId);

        /// <summary>Updates a pet in the store with form data</summary>
        /// <param name="petId">ID of pet that needs to be updated</param>
        /// <param name="name">Name of pet that needs to be updated</param>
        /// <param name="status">Status of pet that needs to be updated</param>
        /// <returns>A <see cref="Task"/> that completes when the request is finished.</returns>
        /// <exception cref="ApiException">
        /// Thrown when the request returns a non-success status code:
        /// <list type="table">
        /// <listheader>
        /// <term>Status</term>
        /// <description>Description</description>
        /// </listheader>
        /// <item>
        /// <term>405</term>
        /// <description>Invalid input</description>
        /// </item>
        /// </list>
        /// </exception>
        [Post("/pet/{petId}")]
        Task UpdatePetWithForm(long petId, [Query] string name, [Query] string status);

        /// <summary>Deletes a pet</summary>
        /// <param name="petId">Pet id to delete</param>
        /// <returns>A <see cref="Task"/> that completes when the request is finished.</returns>
        /// <exception cref="ApiException">
        /// Thrown when the request returns a non-success status code:
        /// <list type="table">
        /// <listheader>
        /// <term>Status</term>
        /// <description>Description</description>
        /// </listheader>
        /// <item>
        /// <term>400</term>
        /// <description>Invalid pet value</description>
        /// </item>
        /// </list>
        /// </exception>
        [Delete("/pet/{petId}")]
        Task DeletePet(long petId, [Header("api_key")] string api_key);

        /// <summary>uploads an image</summary>
        /// <param name="petId">ID of pet to update</param>
        /// <param name="additionalMetadata">Additional Metadata</param>
        /// <returns>
        /// A <see cref="Task"/> representing the <see cref="IApiResponse"/> instance containing the result:
        /// <list type="table">
        /// <listheader>
        /// <term>Status</term>
        /// <description>Description</description>
        /// </listheader>
        /// <item>
        /// <term>200</term>
        /// <description>successful operation</description>
        /// </item>
        /// </list>
        /// </returns>
        [Headers("Accept: application/json")]
        [Post("/pet/{petId}/uploadImage")]
        Task<ApiResponse> UploadFile(long petId, [Query] string additionalMetadata,  StreamPart body);

        /// <summary>Returns pet inventories by status</summary>
        /// <remarks>Returns a map of status codes to quantities</remarks>
        /// <returns>successful operation</returns>
        /// <exception cref="ApiException">Thrown when the request returns a non-success status code.</exception>
        [Headers("Accept: application/json")]
        [Get("/store/inventory")]
        Task<IDictionary<string, int>> GetInventory();

        /// <summary>Place an order for a pet</summary>
        /// <remarks>Place a new order in the store</remarks>
        /// <returns>successful operation</returns>
        /// <exception cref="ApiException">
        /// Thrown when the request returns a non-success status code:
        /// <list type="table">
        /// <listheader>
        /// <term>Status</term>
        /// <description>Description</description>
        /// </listheader>
        /// <item>
        /// <term>405</term>
        /// <description>Invalid input</description>
        /// </item>
        /// </list>
        /// </exception>
        [Headers("Accept: application/json")]
        [Post("/store/order")]
        Task<Order> PlaceOrder([Body] Order body);

        /// <summary>Find purchase order by ID</summary>
        /// <remarks>For valid response try integer IDs with value <= 5 or > 10. Other values will generated exceptions</remarks>
        /// <param name="orderId">ID of order that needs to be fetched</param>
        /// <returns>successful operation</returns>
        /// <exception cref="ApiException">
        /// Thrown when the request returns a non-success status code:
        /// <list type="table">
        /// <listheader>
        /// <term>Status</term>
        /// <description>Description</description>
        /// </listheader>
        /// <item>
        /// <term>400</term>
        /// <description>Invalid ID supplied</description>
        /// </item>
        /// <item>
        /// <term>404</term>
        /// <description>Order not found</description>
        /// </item>
        /// </list>
        /// </exception>
        [Headers("Accept: application/json")]
        [Get("/store/order/{orderId}")]
        Task<Order> GetOrderById(long orderId);

        /// <summary>Delete purchase order by ID</summary>
        /// <remarks>For valid response try integer IDs with value < 1000. Anything above 1000 or nonintegers will generate API errors</remarks>
        /// <param name="orderId">ID of the order that needs to be deleted</param>
        /// <returns>A <see cref="Task"/> that completes when the request is finished.</returns>
        /// <exception cref="ApiException">
        /// Thrown when the request returns a non-success status code:
        /// <list type="table">
        /// <listheader>
        /// <term>Status</term>
        /// <description>Description</description>
        /// </listheader>
        /// <item>
        /// <term>400</term>
        /// <description>Invalid ID supplied</description>
        /// </item>
        /// <item>
        /// <term>404</term>
        /// <description>Order not found</description>
        /// </item>
        /// </list>
        /// </exception>
        [Delete("/store/order/{orderId}")]
        Task DeleteOrder(long orderId);

        /// <summary>Create user</summary>
        /// <remarks>This can only be done by the logged in user.</remarks>
        /// <param name="body">Created user object</param>
        /// <returns>successful operation</returns>
        /// <exception cref="ApiException">Thrown when the request returns a non-success status code.</exception>
        [Headers("Accept: application/json, application/xml")]
        [Post("/user")]
        Task CreateUser([Body] User body);

        /// <summary>Creates list of users with given input array</summary>
        /// <remarks>Creates list of users with given input array</remarks>
        /// <returns>Successful operation</returns>
        /// <exception cref="ApiException">Thrown when the request returns a non-success status code.</exception>
        [Headers("Accept: application/xml, application/json")]
        [Post("/user/createWithList")]
        Task<User> CreateUsersWithListInput([Body] IEnumerable<User> body);

        /// <summary>Logs user into the system</summary>
        /// <param name="username">The user name for login</param>
        /// <param name="password">The password for login in clear text</param>
        /// <returns>successful operation</returns>
        /// <exception cref="ApiException">
        /// Thrown when the request returns a non-success status code:
        /// <list type="table">
        /// <listheader>
        /// <term>Status</term>
        /// <description>Description</description>
        /// </listheader>
        /// <item>
        /// <term>400</term>
        /// <description>Invalid username/password supplied</description>
        /// </item>
        /// </list>
        /// </exception>
        [Headers("Accept: application/json")]
        [Get("/user/login")]
        Task<string> LoginUser([Query] string username, [Query] string password);

        /// <summary>Logs out current logged in user session</summary>
        /// <returns>A <see cref="Task"/> that completes when the request is finished.</returns>
        /// <exception cref="ApiException">Thrown when the request returns a non-success status code.</exception>
        [Get("/user/logout")]
        Task LogoutUser();

        /// <summary>Get user by user name</summary>
        /// <param name="username">The name that needs to be fetched. Use user1 for testing.</param>
        /// <returns>successful operation</returns>
        /// <exception cref="ApiException">
        /// Thrown when the request returns a non-success status code:
        /// <list type="table">
        /// <listheader>
        /// <term>Status</term>
        /// <description>Description</description>
        /// </listheader>
        /// <item>
        /// <term>400</term>
        /// <description>Invalid username supplied</description>
        /// </item>
        /// <item>
        /// <term>404</term>
        /// <description>User not found</description>
        /// </item>
        /// </list>
        /// </exception>
        [Headers("Accept: application/json")]
        [Get("/user/{username}")]
        Task<User> GetUserByName(string username);

        /// <summary>Update user</summary>
        /// <remarks>This can only be done by the logged in user.</remarks>
        /// <param name="username">name that need to be deleted</param>
        /// <param name="body">Update an existent user in the store</param>
        /// <returns>A <see cref="Task"/> that completes when the request is finished.</returns>
        /// <exception cref="ApiException">Thrown when the request returns a non-success status code.</exception>
        [Put("/user/{username}")]
        Task UpdateUser(string username, [Body] User body);

        /// <summary>Delete user</summary>
        /// <remarks>This can only be done by the logged in user.</remarks>
        /// <param name="username">The name that needs to be deleted</param>
        /// <returns>A <see cref="Task"/> that completes when the request is finished.</returns>
        /// <exception cref="ApiException">
        /// Thrown when the request returns a non-success status code:
        /// <list type="table">
        /// <listheader>
        /// <term>Status</term>
        /// <description>Description</description>
        /// </listheader>
        /// <item>
        /// <term>400</term>
        /// <description>Invalid username supplied</description>
        /// </item>
        /// <item>
        /// <term>404</term>
        /// <description>User not found</description>
        /// </item>
        /// </list>
        /// </exception>
        [Delete("/user/{username}")]
        Task DeleteUser(string username);
    }
}

Here's an example generated output from the Swagger Petstore example configured to wrap the return type in IApiResponse<T>

CLI Tool

$ refitter ./openapi.json --namespace "Your.Namespace.Of.Choice.GeneratedCode" --use-api-response

Source Generator **.refitter file**

{
  "openApiPath": "./openapi.json",
  "namespace": "Your.Namespace.Of.Choice.GeneratedCode",
  "returnIApiResponse": true
}

Output

using Refit;
using System.Collections.Generic;
using System.Text.Json.Serialization;
using System.Threading.Tasks;

namespace Your.Namespace.Of.Choice.GeneratedCode
{
    [System.CodeDom.Compiler.GeneratedCode("Refitter", "1.0.0.0")]
    public partial interface ISwaggerPetstore
    {
        /// <summary>Update an existing pet</summary>
        /// <remarks>Update an existing pet by Id</remarks>
        /// <param name="body">Update an existent pet in the store</param>
        /// <returns>
        /// A <see cref="Task"/> representing the <see cref="IApiResponse"/> instance containing the result:
        /// <list type="table">
        /// <listheader>
        /// <term>Status</term>
        /// <description>Description</description>
        /// </listheader>
        /// <item>
        /// <term>200</term>
        /// <description>Successful operation</description>
        /// </item>
        /// <item>
        /// <term>400</term>
        /// <description>Invalid ID supplied</description>
        /// </item>
        /// <item>
        /// <term>404</term>
        /// <description>Pet not found</description>
        /// </item>
        /// <item>
        /// <term>405</term>
        /// <description>Validation exception</description>
        /// </item>
        /// </list>
        /// </returns>
        [Headers("Accept: application/xml, application/json")]
        [Put("/pet")]
        Task<IApiResponse<Pet>> UpdatePet([Body] Pet body);

        /// <summary>Add a new pet to the store</summary>
        /// <remarks>Add a new pet to the store</remarks>
        /// <param name="body">Create a new pet in the store</param>
        /// <returns>
        /// A <see cref="Task"/> representing the <see cref="IApiResponse"/> instance containing the result:
        /// <list type="table">
        /// <listheader>
        /// <term>Status</term>
        /// <description>Description</description>
        /// </listheader>
        /// <item>
        /// <term>200</term>
        /// <description>Successful operation</description>
        /// </item>
        /// <item>
        /// <term>405</term>
        /// <description>Invalid input</description>
        /// </item>
        /// </list>
        /// </returns>
        [Headers("Accept: application/xml, application/json")]
        [Post("/pet")]
        Task<IApiResponse<Pet>> AddPet([Body] Pet body);

        /// <summary>Finds Pets by status</summary>
        /// <remarks>Multiple status values can be provided with comma separated strings</remarks>
        /// <param name="status">Status values that need to be considered for filter</param>
        /// <returns>
        /// A <see cref="Task"/> representing the <see cref="IApiResponse"/> instance containing the result:
        /// <list type="table">
        /// <listheader>
        /// <term>Status</term>
        /// <description>Description</description>
        /// </listheader>
        /// <item>
        /// <term>200</term>
        /// <description>successful operation</description>
        /// </item>
        /// <item>
        /// <term>400</term>
        /// <description>Invalid status value</description>
        /// </item>
        /// </list>
        /// </returns>
        [Headers("Accept: application/json")]
        [Get("/pet/findByStatus")]
        Task<IApiResponse<ICollection<Pet>>> FindPetsByStatus([Query] Status? status);

        /// <summary>Finds Pets by tags</summary>
        /// <remarks>Multiple tags can be provided with comma separated strings. Use tag1, tag2, tag3 for testing.</remarks>
        /// <param name="tags">Tags to filter by</param>
        /// <returns>
        /// A <see cref="Task"/> representing the <see cref="IApiResponse"/> instance containing the result:
        /// <list type="table">
        /// <listheader>
        /// <term>Status</term>
        /// <description>Description</description>
        /// </listheader>
        /// <item>
        /// <term>200</term>
        /// <description>successful operation</description>
        /// </item>
        /// <item>
        /// <term>400</term>
        /// <description>Invalid tag value</description>
        /// </item>
        /// </list>
        /// </returns>
        [Headers("Accept: application/json")]
        [Get("/pet/findByTags")]
        Task<IApiResponse<ICollection<Pet>>> FindPetsByTags([Query(CollectionFormat.Multi)] IEnumerable<string> tags);

        /// <summary>Find pet by ID</summary>
        /// <remarks>Returns a single pet</remarks>
        /// <param name="petId">ID of pet to return</param>
        /// <returns>
        /// A <see cref="Task"/> representing the <see cref="IApiResponse"/> instance containing the result:
        /// <list type="table">
        /// <listheader>
        /// <term>Status</term>
        /// <description>Description</description>
        /// </listheader>
        /// <item>
        /// <term>200</term>
        /// <description>successful operation</description>
        /// </item>
        /// <item>
        /// <term>400</term>
        /// <description>Invalid ID supplied</description>
        /// </item>
        /// <item>
        /// <term>404</term>
        /// <description>Pet not found</description>
        /// </item>
        /// </list>
        /// </returns>
        [Headers("Accept: application/xml, application/json")]
        [Get("/pet/{petId}")]
        Task<IApiResponse<Pet>> GetPetById(long petId);

        /// <summary>Updates a pet in the store with form data</summary>
        /// <param name="petId">ID of pet that needs to be updated</param>
        /// <param name="name">Name of pet that needs to be updated</param>
        /// <param name="status">Status of pet that needs to be updated</param>
        /// <returns>
        /// A <see cref="Task"/> representing the <see cref="IApiResponse"/> instance containing the result:
        /// <list type="table">
        /// <listheader>
        /// <term>Status</term>
        /// <description>Description</description>
        /// </listheader>
        /// <item>
        /// <term>405</term>
        /// <description>Invalid input</description>
        /// </item>
        /// </list>
        /// </returns>
        [Post("/pet/{petId}")]
        Task<IApiResponse> UpdatePetWithForm(long petId, [Query] string name, [Query] string status);

        /// <summary>Deletes a pet</summary>
        /// <param name="petId">Pet id to delete</param>
        /// <returns>
        /// A <see cref="Task"/> representing the <see cref="IApiResponse"/> instance containing the result:
        /// <list type="table">
        /// <listheader>
        /// <term>Status</term>
        /// <description>Description</description>
        /// </listheader>
        /// <item>
        /// <term>400</term>
        /// <description>Invalid pet value</description>
        /// </item>
        /// </list>
        /// </returns>
        [Delete("/pet/{petId}")]
        Task<IApiResponse> DeletePet(long petId, [Header("api_key")] string api_key);

        /// <summary>uploads an image</summary>
        /// <param name="petId">ID of pet to update</param>
        /// <param name="additionalMetadata">Additional Metadata</param>
        /// <returns>
        /// A <see cref="Task"/> representing the <see cref="IApiResponse"/> instance containing the result:
        /// <list type="table">
        /// <listheader>
        /// <term>Status</term>
        /// <description>Description</description>
        /// </listheader>
        /// <item>
        /// <term>200</term>
        /// <description>successful operation</description>
        /// </item>
        /// </list>
        /// </returns>
        [Headers("Accept: application/json")]
        [Post("/pet/{petId}/uploadImage")]
        Task<IApiResponse<ApiResponse>> UploadFile(long petId, [Query] string additionalMetadata,  StreamPart body);

        /// <summary>Returns pet inventories by status</summary>
        /// <remarks>Returns a map of status codes to quantities</remarks>
        /// <returns>successful operation</returns>
        /// <exception cref="ApiException">Thrown when the request returns a non-success status code.</exception>
        [Headers("Accept: application/json")]
        [Get("/store/inventory")]
        Task<IApiResponse<IDictionary<string, int>>> GetInventory();

        /// <summary>Place an order for a pet</summary>
        /// <remarks>Place a new order in the store</remarks>
        /// <returns>
        /// A <see cref="Task"/> representing the <see cref="IApiResponse"/> instance containing the result:
        /// <list type="table">
        /// <listheader>
        /// <term>Status</term>
        /// <description>Description</description>
        /// </listheader>
        /// <item>
        /// <term>200</term>
        /// <description>successful operation</description>
        /// </item>
        /// <item>
        /// <term>405</term>
        /// <description>Invalid input</description>
        /// </item>
        /// </list>
        /// </returns>
        [Headers("Accept: application/json")]
        [Post("/store/order")]
        Task<IApiResponse<Order>> PlaceOrder([Body] Order body);

        /// <summary>Find purchase order by ID</summary>
        /// <remarks>For valid response try integer IDs with value <= 5 or > 10. Other values will generated exceptions</remarks>
        /// <param name="orderId">ID of order that needs to be fetched</param>
        /// <returns>
        /// A <see cref="Task"/> representing the <see cref="IApiResponse"/> instance containing the result:
        /// <list type="table">
        /// <listheader>
        /// <term>Status</term>
        /// <description>Description</description>
        /// </listheader>
        /// <item>
        /// <term>200</term>
        /// <description>successful operation</description>
        /// </item>
        /// <item>
        /// <term>400</term>
        /// <description>Invalid ID supplied</description>
        /// </item>
        /// <item>
        /// <term>404</term>
        /// <description>Order not found</description>
        /// </item>
        /// </list>
        /// </returns>
        [Headers("Accept: application/json")]
        [Get("/store/order/{orderId}")]
        Task<IApiResponse<Order>> GetOrderById(long orderId);

        /// <summary>Delete purchase order by ID</summary>
        /// <remarks>For valid response try integer IDs with value < 1000. Anything above 1000 or nonintegers will generate API errors</remarks>
        /// <param name="orderId">ID of the order that needs to be deleted</param>
        /// <returns>
        /// A <see cref="Task"/> representing the <see cref="IApiResponse"/> instance containing the result:
        /// <list type="table">
        /// <listheader>
        /// <term>Status</term>
        /// <description>Description</description>
        /// </listheader>
        /// <item>
        /// <term>400</term>
        /// <description>Invalid ID supplied</description>
        /// </item>
        /// <item>
        /// <term>404</term>
        /// <description>Order not found</description>
        /// </item>
        /// </list>
        /// </returns>
        [Delete("/store/order/{orderId}")]
        Task<IApiResponse> DeleteOrder(long orderId);

        /// <summary>Create user</summary>
        /// <remarks>This can only be done by the logged in user.</remarks>
        /// <param name="body">Created user object</param>
        /// <returns>A <see cref="Task"/> representing the <see cref="IApiResponse"/> instance containing the result.</returns>
        [Headers("Accept: application/json, application/xml")]
        [Post("/user")]
        Task<IApiResponse> CreateUser([Body] User body);

        /// <summary>Creates list of users with given input array</summary>
        /// <remarks>Creates list of users with given input array</remarks>
        /// <returns>
        /// A <see cref="Task"/> representing the <see cref="IApiResponse"/> instance containing the result:
        /// <list type="table">
        /// <listheader>
        /// <term>Status</term>
        /// <description>Description</description>
        /// </listheader>
        /// <item>
        /// <term>200</term>
        /// <description>Successful operation</description>
        /// </item>
        /// </list>
        /// </returns>
        [Headers("Accept: application/xml, application/json")]
        [Post("/user/createWithList")]
        Task<IApiResponse<User>> CreateUsersWithListInput([Body] IEnumerable<User> body);

        /// <summary>Logs user into the system</summary>
        /// <param name="username">The user name for login</param>
        /// <param name="password">The password for login in clear text</param>
        /// <returns>
        /// A <see cref="Task"/> representing the <see cref="IApiResponse"/> instance containing the result:
        /// <list type="table">
        /// <listheader>
        /// <term>Status</term>
        /// <description>Description</description>
        /// </listheader>
        /// <item>
        /// <term>200</term>
        /// <description>successful operation</description>
        /// </item>
        /// <item>
        /// <term>400</term>
        /// <description>Invalid username/password supplied</description>
        /// </item>
        /// </list>
        /// </returns>
        [Headers("Accept: application/json")]
        [Get("/user/login")]
        Task<IApiResponse<string>> LoginUser([Query] string username, [Query] string password);

        /// <summary>Logs out current logged in user session</summary>
        /// <returns>A <see cref="Task"/> representing the <see cref="IApiResponse"/> instance containing the result.</returns>
        [Get("/user/logout")]
        Task<IApiResponse> LogoutUser();

        /// <summary>Get user by user name</summary>
        /// <param name="username">The name that needs to be fetched. Use user1 for testing.</param>
        /// <returns>
        /// A <see cref="Task"/> representing the <see cref="IApiResponse"/> instance containing the result:
        /// <list type="table">
        /// <listheader>
        /// <term>Status</term>
        /// <description>Description</description>
        /// </listheader>
        /// <item>
        /// <term>200</term>
        /// <description>successful operation</description>
        /// </item>
        /// <item>
        /// <term>400</term>
        /// <description>Invalid username supplied</description>
        /// </item>
        /// <item>
        /// <term>404</term>
        /// <description>User not found</description>
        /// </item>
        /// </list>
        /// </returns>
        [Headers("Accept: application/json")]
        [Get("/user/{username}")]
        Task<IApiResponse<User>> GetUserByName(string username);

        /// <summary>Update user</summary>
        /// <remarks>This can only be done by the logged in user.</remarks>
        /// <param name="username">name that need to be deleted</param>
        /// <param name="body">Update an existent user in the store</param>
        /// <returns>A <see cref="Task"/> representing the <see cref="IApiResponse"/> instance containing the result.</returns>
        [Put("/user/{username}")]
        Task<IApiResponse> UpdateUser(string username, [Body] User body);

        /// <summary>Delete user</summary>
        /// <remarks>This can only be done by the logged in user.</remarks>
        /// <param name="username">The name that needs to be deleted</param>
        /// <returns>
        /// A <see cref="Task"/> representing the <see cref="IApiResponse"/> instance containing the result:
        /// <list type="table">
        /// <listheader>
        /// <term>Status</term>
        /// <description>Description</description>
        /// </listheader>
        /// <item>
        /// <term>400</term>
        /// <description>Invalid username supplied</description>
        /// </item>
        /// <item>
        /// <term>404</term>
        /// <description>User not found</description>
        /// </item>
        /// </list>
        /// </returns>
        [Delete("/user/{username}")]
        Task<IApiResponse> DeleteUser(string username);
    }
}

Here's an example generated output from the Swagger Petstore example configured to generate an interface for each endpoint

CLI Tool

$ refitter ./openapi.json --namespace "Your.Namespace.Of.Choice.GeneratedCode" --multiple-interfaces ByEndpoint

Source Generator **.refitter file**

{
  "openApiPath": "./openapi.json",
  "namespace": "Your.Namespace.Of.Choice.GeneratedCode",
  "multipleInterfaces": "ByEndpoint"
}

Output

/// <summary>Update an existing pet</summary>
[System.CodeDom.Compiler.GeneratedCode("Refitter", "1.0.0.0")]
public partial interface IUpdatePetEndpoint
{
    /// <summary>Update an existing pet</summary>
    /// <remarks>Update an existing pet by Id</remarks>
    /// <param name="body">Update an existent pet in the store</param>
    /// <returns>Successful operation</returns>
    /// <exception cref="ApiException">
    /// Thrown when the request returns a non-success status code:
    /// <list type="table">
    /// <listheader>
    /// <term>Status</term>
    /// <description>Description</description>
    /// </listheader>
    /// <item>
    /// <term>400</term>
    /// <description>Invalid ID supplied</description>
    /// </item>
    /// <item>
    /// <term>404</term>
    /// <description>Pet not found</description>
    /// </item>
    /// <item>
    /// <term>405</term>
    /// <description>Validation exception</description>
    /// </item>
    /// </list>
    /// </exception>
    [Headers("Accept: application/xml, application/json")]
    [Put("/pet")]
    Task<Pet> Execute([Body] Pet body);
}

/// <summary>Add a new pet to the store</summary>
[System.CodeDom.Compiler.GeneratedCode("Refitter", "1.0.0.0")]
public partial interface IAddPetEndpoint
{
    /// <summary>Add a new pet to the store</summary>
    /// <remarks>Add a new pet to the store</remarks>
    /// <param name="body">Create a new pet in the store</param>
    /// <returns>Successful operation</returns>
    /// <exception cref="ApiException">
    /// Thrown when the request returns a non-success status code:
    /// <list type="table">
    /// <listheader>
    /// <term>Status</term>
    /// <description>Description</description>
    /// </listheader>
    /// <item>
    /// <term>405</term>
    /// <description>Invalid input</description>
    /// </item>
    /// </list>
    /// </exception>
    [Headers("Accept: application/xml, application/json")]
    [Post("/pet")]
    Task<Pet> Execute([Body] Pet body);
}

/// <summary>Finds Pets by status</summary>
[System.CodeDom.Compiler.GeneratedCode("Refitter", "1.0.0.0")]
public partial interface IFindPetsByStatusEndpoint
{
    /// <summary>Finds Pets by status</summary>
    /// <remarks>Multiple status values can be provided with comma separated strings</remarks>
    /// <param name="status">Status values that need to be considered for filter</param>
    /// <returns>successful operation</returns>
    /// <exception cref="ApiException">
    /// Thrown when the request returns a non-success status code:
    /// <list type="table">
    /// <listheader>
    /// <term>Status</term>
    /// <description>Description</description>
    /// </listheader>
    /// <item>
    /// <term>400</term>
    /// <description>Invalid status value</description>
    /// </item>
    /// </list>
    /// </exception>
    [Headers("Accept: application/json")]
    [Get("/pet/findByStatus")]
    Task<ICollection<Pet>> Execute([Query] Status? status);
}

/// <summary>Finds Pets by tags</summary>
[System.CodeDom.Compiler.GeneratedCode("Refitter", "1.0.0.0")]
public partial interface IFindPetsByTagsEndpoint
{
    /// <summary>Finds Pets by tags</summary>
    /// <remarks>Multiple tags can be provided with comma separated strings. Use tag1, tag2, tag3 for testing.</remarks>
    /// <param name="tags">Tags to filter by</param>
    /// <returns>successful operation</returns>
    /// <exception cref="ApiException">
    /// Thrown when the request returns a non-success status code:
    /// <list type="table">
    /// <listheader>
    /// <term>Status</term>
    /// <description>Description</description>
    /// </listheader>
    /// <item>
    /// <term>400</term>
    /// <description>Invalid tag value</description>
    /// </item>
    /// </list>
    /// </exception>
    [Headers("Accept: application/json")]
    [Get("/pet/findByTags")]
    Task<ICollection<Pet>> Execute([Query(CollectionFormat.Multi)] IEnumerable<string> tags);
}

/// <summary>Find pet by ID</summary>
[System.CodeDom.Compiler.GeneratedCode("Refitter", "1.0.0.0")]
public partial interface IGetPetByIdEndpoint
{
    /// <summary>Find pet by ID</summary>
    /// <remarks>Returns a single pet</remarks>
    /// <param name="petId">ID of pet to return</param>
    /// <returns>successful operation</returns>
    /// <exception cref="ApiException">
    /// Thrown when the request returns a non-success status code:
    /// <list type="table">
    /// <listheader>
    /// <term>Status</term>
    /// <description>Description</description>
    /// </listheader>
    /// <item>
    /// <term>400</term>
    /// <description>Invalid ID supplied</description>
    /// </item>
    /// <item>
    /// <term>404</term>
    /// <description>Pet not found</description>
    /// </item>
    /// </list>
    /// </exception>
    [Headers("Accept: application/xml, application/json")]
    [Get("/pet/{petId}")]
    Task<Pet> Execute(long petId);
}

/// <summary>Updates a pet in the store with form data</summary>
[System.CodeDom.Compiler.GeneratedCode("Refitter", "1.0.0.0")]
public partial interface IUpdatePetWithFormEndpoint
{
    /// <summary>Updates a pet in the store with form data</summary>
    /// <param name="petId">ID of pet that needs to be updated</param>
    /// <param name="name">Name of pet that needs to be updated</param>
    /// <param name="status">Status of pet that needs to be updated</param>
    /// <returns>A <see cref="Task"/> that completes when the request is finished.</returns>
    /// <exception cref="ApiException">
    /// Thrown when the request returns a non-success status code:
    /// <list type="table">
    /// <listheader>
    /// <term>Status</term>
    /// <description>Description</description>
    /// </listheader>
    /// <item>
    /// <term>405</term>
    /// <description>Invalid input</description>
    /// </item>
    /// </list>
    /// </exception>
    [Post("/pet/{petId}")]
    Task Execute(long petId, [Query] string name, [Query] string status);
}

/// <summary>Deletes a pet</summary>
[System.CodeDom.Compiler.GeneratedCode("Refitter", "1.0.0.0")]
public partial interface IDeletePetEndpoint
{
    /// <summary>Deletes a pet</summary>
    /// <param name="petId">Pet id to delete</param>
    /// <returns>A <see cref="Task"/> that completes when the request is finished.</returns>
    /// <exception cref="ApiException">
    /// Thrown when the request returns a non-success status code:
    /// <list type="table">
    /// <listheader>
    /// <term>Status</term>
    /// <description>Description</description>
    /// </listheader>
    /// <item>
    /// <term>400</term>
    /// <description>Invalid pet value</description>
    /// </item>
    /// </list>
    /// </exception>
    [Delete("/pet/{petId}")]
    Task Execute(long petId, [Header("api_key")] string api_key);
}

/// <summary>uploads an image</summary>
[System.CodeDom.Compiler.GeneratedCode("Refitter", "1.0.0.0")]
public partial interface IUploadFileEndpoint
{
    /// <summary>uploads an image</summary>
    /// <param name="petId">ID of pet to update</param>
    /// <param name="additionalMetadata">Additional Metadata</param>
    /// <returns>
    /// A <see cref="Task"/> representing the <see cref="IApiResponse"/> instance containing the result:
    /// <list type="table">
    /// <listheader>
    /// <term>Status</term>
    /// <description>Description</description>
    /// </listheader>
    /// <item>
    /// <term>200</term>
    /// <description>successful operation</description>
    /// </item>
    /// </list>
    /// </returns>
    [Headers("Accept: application/json")]
    [Post("/pet/{petId}/uploadImage")]
    Task<ApiResponse> Execute(long petId, [Query] string additionalMetadata,  StreamPart body);
}

/// <summary>Returns pet inventories by status</summary>
[System.CodeDom.Compiler.GeneratedCode("Refitter", "1.0.0.0")]
public partial interface IGetInventoryEndpoint
{
    /// <summary>Returns pet inventories by status</summary>
    /// <remarks>Returns a map of status codes to quantities</remarks>
    /// <returns>successful operation</returns>
    /// <exception cref="ApiException">Thrown when the request returns a non-success status code.</exception>
    [Headers("Accept: application/json")]
    [Get("/store/inventory")]
    Task<IDictionary<string, int>> Execute();
}

/// <summary>Place an order for a pet</summary>
[System.CodeDom.Compiler.GeneratedCode("Refitter", "1.0.0.0")]
public partial interface IPlaceOrderEndpoint
{
    /// <summary>Place an order for a pet</summary>
    /// <remarks>Place a new order in the store</remarks>
    /// <returns>successful operation</returns>
    /// <exception cref="ApiException">
    /// Thrown when the request returns a non-success status code:
    /// <list type="table">
    /// <listheader>
    /// <term>Status</term>
    /// <description>Description</description>
    /// </listheader>
    /// <item>
    /// <term>405</term>
    /// <description>Invalid input</description>
    /// </item>
    /// </list>
    /// </exception>
    [Headers("Accept: application/json")]
    [Post("/store/order")]
    Task<Order> Execute([Body] Order body);
}

/// <summary>Find purchase order by ID</summary>
[System.CodeDom.Compiler.GeneratedCode("Refitter", "1.0.0.0")]
public partial interface IGetOrderByIdEndpoint
{
    /// <summary>Find purchase order by ID</summary>
    /// <remarks>For valid response try integer IDs with value <= 5 or > 10. Other values will generated exceptions</remarks>
    /// <param name="orderId">ID of order that needs to be fetched</param>
    /// <returns>successful operation</returns>
    /// <exception cref="ApiException">
    /// Thrown when the request returns a non-success status code:
    /// <list type="table">
    /// <listheader>
    /// <term>Status</term>
    /// <description>Description</description>
    /// </listheader>
    /// <item>
    /// <term>400</term>
    /// <description>Invalid ID supplied</description>
    /// </item>
    /// <item>
    /// <term>404</term>
    /// <description>Order not found</description>
    /// </item>
    /// </list>
    /// </exception>
    [Headers("Accept: application/json")]
    [Get("/store/order/{orderId}")]
    Task<Order> Execute(long orderId);
}

/// <summary>Delete purchase order by ID</summary>
[System.CodeDom.Compiler.GeneratedCode("Refitter", "1.0.0.0")]
public partial interface IDeleteOrderEndpoint
{
    /// <summary>Delete purchase order by ID</summary>
    /// <remarks>For valid response try integer IDs with value < 1000. Anything above 1000 or nonintegers will generate API errors</remarks>
    /// <param name="orderId">ID of the order that needs to be deleted</param>
    /// <returns>A <see cref="Task"/> that completes when the request is finished.</returns>
    /// <exception cref="ApiException">
    /// Thrown when the request returns a non-success status code:
    /// <list type="table">
    /// <listheader>
    /// <term>Status</term>
    /// <description>Description</description>
    /// </listheader>
    /// <item>
    /// <term>400</term>
    /// <description>Invalid ID supplied</description>
    /// </item>
    /// <item>
    /// <term>404</term>
    /// <description>Order not found</description>
    /// </item>
    /// </list>
    /// </exception>
    [Delete("/store/order/{orderId}")]
    Task Execute(long orderId);
}

/// <summary>Create user</summary>
[System.CodeDom.Compiler.GeneratedCode("Refitter", "1.0.0.0")]
public partial interface ICreateUserEndpoint
{
    /// <summary>Create user</summary>
    /// <remarks>This can only be done by the logged in user.</remarks>
    /// <param name="body">Created user object</param>
    /// <returns>successful operation</returns>
    /// <exception cref="ApiException">Thrown when the request returns a non-success status code.</exception>
    [Headers("Accept: application/json, application/xml")]
    [Post("/user")]
    Task Execute([Body] User body);
}

/// <summary>Creates list of users with given input array</summary>
[System.CodeDom.Compiler.GeneratedCode("Refitter", "1.0.0.0")]
public partial interface ICreateUsersWithListInputEndpoint
{
    /// <summary>Creates list of users with given input array</summary>
    /// <remarks>Creates list of users with given input array</remarks>
    /// <returns>Successful operation</returns>
    /// <exception cref="ApiException">Thrown when the request returns a non-success status code.</exception>
    [Headers("Accept: application/xml, application/json")]
    [Post("/user/createWithList")]
    Task<User> Execute([Body] IEnumerable<User> body);
}

/// <summary>Logs user into the system</summary>
[System.CodeDom.Compiler.GeneratedCode("Refitter", "1.0.0.0")]
public partial interface ILoginUserEndpoint
{
    /// <summary>Logs user into the system</summary>
    /// <param name="username">The user name for login</param>
    /// <param name="password">The password for login in clear text</param>
    /// <returns>successful operation</returns>
    /// <exception cref="ApiException">
    /// Thrown when the request returns a non-success status code:
    /// <list type="table">
    /// <listheader>
    /// <term>Status</term>
    /// <description>Description</description>
    /// </listheader>
    /// <item>
    /// <term>400</term>
    /// <description>Invalid username/password supplied</description>
    /// </item>
    /// </list>
    /// </exception>
    [Headers("Accept: application/json")]
    [Get("/user/login")]
    Task<string> Execute([Query] string username, [Query] string password);
}

/// <summary>Logs out current logged in user session</summary>
[System.CodeDom.Compiler.GeneratedCode("Refitter", "1.0.0.0")]
public partial interface ILogoutUserEndpoint
{
    /// <summary>Logs out current logged in user session</summary>
    /// <returns>A <see cref="Task"/> that completes when the request is finished.</returns>
    /// <exception cref="ApiException">Thrown when the request returns a non-success status code.</exception>
    [Get("/user/logout")]
    Task Execute();
}

/// <summary>Get user by user name</summary>
[System.CodeDom.Compiler.GeneratedCode("Refitter", "1.0.0.0")]
public partial interface IGetUserByNameEndpoint
{
    /// <summary>Get user by user name</summary>
    /// <param name="username">The name that needs to be fetched. Use user1 for testing.</param>
    /// <returns>successful operation</returns>
    /// <exception cref="ApiException">
    /// Thrown when the request returns a non-success status code:
    /// <list type="table">
    /// <listheader>
    /// <term>Status</term>
    /// <description>Description</description>
    /// </listheader>
    /// <item>
    /// <term>400</term>
    /// <description>Invalid username supplied</description>
    /// </item>
    /// <item>
    /// <term>404</term>
    /// <description>User not found</description>
    /// </item>
    /// </list>
    /// </exception>
    [Headers("Accept: application/json")]
    [Get("/user/{username}")]
    Task<User> Execute(string username);
}

/// <summary>Update user</summary>
[System.CodeDom.Compiler.GeneratedCode("Refitter", "1.0.0.0")]
public partial interface IUpdateUserEndpoint
{
    /// <summary>Update user</summary>
    /// <remarks>This can only be done by the logged in user.</remarks>
    /// <param name="username">name that need to be deleted</param>
    /// <param name="body">Update an existent user in the store</param>
    /// <returns>A <see cref="Task"/> that completes when the request is finished.</returns>
    /// <exception cref="ApiException">Thrown when the request returns a non-success status code.</exception>
    [Put("/user/{username}")]
    Task Execute(string username, [Body] User body);
}

/// <summary>Delete user</summary>
[System.CodeDom.Compiler.GeneratedCode("Refitter", "1.0.0.0")]
public partial interface IDeleteUserEndpoint
{
    /// <summary>Delete user</summary>
    /// <remarks>This can only be done by the logged in user.</remarks>
    /// <param name="username">The name that needs to be deleted</param>
    /// <returns>A <see cref="Task"/> that completes when the request is finished.</returns>
    /// <exception cref="ApiException">
    /// Thrown when the request returns a non-success status code:
    /// <list type="table">
    /// <listheader>
    /// <term>Status</term>
    /// <description>Description</description>
    /// </listheader>
    /// <item>
    /// <term>400</term>
    /// <description>Invalid username supplied</description>
    /// </item>
    /// <item>
    /// <term>404</term>
    /// <description>User not found</description>
    /// </item>
    /// </list>
    /// </exception>
    [Delete("/user/{username}")]
    Task Execute(string username);
}

Here's an example generated output from the Swagger Petstore example configured to generate an interface with dynamic querystring paremeters

CLI Tool

$ refitter ./openapi.json --namespace "Your.Namespace.Of.Choice.GeneratedCode" --use-dynamic-querystring-parameters

Output

[System.CodeDom.Compiler.GeneratedCode("Refitter", "1.0.0.0")]
public partial interface ISwaggerPetstoreOpenAPI30
{
    /// <summary>Update an existing pet</summary>
    /// <remarks>Update an existing pet by Id</remarks>
    /// <param name="body">Update an existent pet in the store</param>
    /// <returns>Successful operation</returns>
    /// <exception cref="ApiException">
    /// Thrown when the request returns a non-success status code:
    /// <list type="table">
    /// <listheader>
    /// <term>Status</term>
    /// <description>Description</description>
    /// </listheader>
    /// <item>
    /// <term>400</term>
    /// <description>Invalid ID supplied</description>
    /// </item>
    /// <item>
    /// <term>404</term>
    /// <description>Pet not found</description>
    /// </item>
    /// <item>
    /// <term>405</term>
    /// <description>Validation exception</description>
    /// </item>
    /// </list>
    /// </exception>
    [Headers("Accept: application/xml, application/json")]
    [Put("/pet")]
    Task<Pet> UpdatePet([Body] Pet body);

    /// <summary>Add a new pet to the store</summary>
    /// <remarks>Add a new pet to the store</remarks>
    /// <param name="body">Create a new pet in the store</param>
    /// <returns>Successful operation</returns>
    /// <exception cref="ApiException">
    /// Thrown when the request returns a non-success status code:
    /// <list type="table">
    /// <listheader>
    /// <term>Status</term>
    /// <description>Description</description>
    /// </listheader>
    /// <item>
    /// <term>405</term>
    /// <description>Invalid input</description>
    /// </item>
    /// </list>
    /// </exception>
    [Headers("Accept: application/xml, application/json")]
    [Post("/pet")]
    Task<Pet> AddPet([Body] Pet body);

    /// <summary>Finds Pets by status</summary>
    /// <remarks>Multiple status values can be provided with comma separated strings</remarks>
    /// <param name="status">Status values that need to be considered for filter</param>
    /// <returns>successful operation</returns>
    /// <exception cref="ApiException">
    /// Thrown when the request returns a non-success status code:
    /// <list type="table">
    /// <listheader>
    /// <term>Status</term>
    /// <description>Description</description>
    /// </listheader>
    /// <item>
    /// <term>400</term>
    /// <description>Invalid status value</description>
    /// </item>
    /// </list>
    /// </exception>
    [Headers("Accept: application/xml, application/json")]
    [Get("/pet/findByStatus")]
    Task<ICollection<Pet>> FindPetsByStatus([Query] Status? status);

    /// <summary>Finds Pets by tags</summary>
    /// <remarks>Multiple tags can be provided with comma separated strings. Use tag1, tag2, tag3 for testing.</remarks>
    /// <param name="tags">Tags to filter by</param>
    /// <returns>successful operation</returns>
    /// <exception cref="ApiException">
    /// Thrown when the request returns a non-success status code:
    /// <list type="table">
    /// <listheader>
    /// <term>Status</term>
    /// <description>Description</description>
    /// </listheader>
    /// <item>
    /// <term>400</term>
    /// <description>Invalid tag value</description>
    /// </item>
    /// </list>
    /// </exception>
    [Headers("Accept: application/xml, application/json")]
    [Get("/pet/findByTags")]
    Task<ICollection<Pet>> FindPetsByTags([Query(CollectionFormat.Multi)] IEnumerable<string> tags);

    /// <summary>Find pet by ID</summary>
    /// <remarks>Returns a single pet</remarks>
    /// <param name="petId">ID of pet to return</param>
    /// <returns>successful operation</returns>
    /// <exception cref="ApiException">
    /// Thrown when the request returns a non-success status code:
    /// <list type="table">
    /// <listheader>
    /// <term>Status</term>
    /// <description>Description</description>
    /// </listheader>
    /// <item>
    /// <term>400</term>
    /// <description>Invalid ID supplied</description>
    /// </item>
    /// <item>
    /// <term>404</term>
    /// <description>Pet not found</description>
    /// </item>
    /// </list>
    /// </exception>
    [Headers("Accept: application/xml, application/json")]
    [Get("/pet/{petId}")]
    Task<Pet> GetPetById(long petId);

    /// <summary>Updates a pet in the store with form data</summary>
    /// <param name="petId">ID of pet that needs to be updated</param>
    /// <param name="queryParams">The dynamic querystring parameter wrapping all others.</param>
    /// <returns>A <see cref="Task"/> that completes when the request is finished.</returns>
    /// <exception cref="ApiException">
    /// Thrown when the request returns a non-success status code:
    /// <list type="table">
    /// <listheader>
    /// <term>Status</term>
    /// <description>Description</description>
    /// </listheader>
    /// <item>
    /// <term>405</term>
    /// <description>Invalid input</description>
    /// </item>
    /// </list>
    /// </exception>
    [Post("/pet/{petId}")]
    Task UpdatePetWithForm(long petId, [Query] UpdatePetWithFormQueryParams queryParams);

    /// <summary>Deletes a pet</summary>
    /// <param name="petId">Pet id to delete</param>
    /// <returns>A <see cref="Task"/> that completes when the request is finished.</returns>
    /// <exception cref="ApiException">
    /// Thrown when the request returns a non-success status code:
    /// <list type="table">
    /// <listheader>
    /// <term>Status</term>
    /// <description>Description</description>
    /// </listheader>
    /// <item>
    /// <term>400</term>
    /// <description>Invalid pet value</description>
    /// </item>
    /// </list>
    /// </exception>
    [Delete("/pet/{petId}")]
    Task DeletePet(long petId, [Header("api_key")] string api_key);

    /// <summary>uploads an image</summary>
    /// <param name="petId">ID of pet to update</param>
    /// <param name="additionalMetadata">Additional Metadata</param>
    /// <returns>
    /// A <see cref="Task"/> representing the <see cref="IApiResponse"/> instance containing the result:
    /// <list type="table">
    /// <listheader>
    /// <term>Status</term>
    /// <description>Description</description>
    /// </listheader>
    /// <item>
    /// <term>200</term>
    /// <description>successful operation</description>
    /// </item>
    /// </list>
    /// </returns>
    [Headers("Accept: application/json")]
    [Post("/pet/{petId}/uploadImage")]
    Task<ApiResponse> UploadFile(long petId, [Query] string additionalMetadata,  StreamPart body);

    /// <summary>Returns pet inventories by status</summary>
    /// <remarks>Returns a map of status codes to quantities</remarks>
    /// <returns>successful operation</returns>
    /// <exception cref="ApiException">Thrown when the request returns a non-success status code.</exception>
    [Headers("Accept: application/json")]
    [Get("/store/inventory")]
    Task<IDictionary<string, int>> GetInventory();

    /// <summary>Place an order for a pet</summary>
    /// <remarks>Place a new order in the store</remarks>
    /// <returns>successful operation</returns>
    /// <exception cref="ApiException">
    /// Thrown when the request returns a non-success status code:
    /// <list type="table">
    /// <listheader>
    /// <term>Status</term>
    /// <description>Description</description>
    /// </listheader>
    /// <item>
    /// <term>405</term>
    /// <description>Invalid input</description>
    /// </item>
    /// </list>
    /// </exception>
    [Headers("Accept: application/json")]
    [Post("/store/order")]
    Task<Order> PlaceOrder([Body] Order body);

    /// <summary>Find purchase order by ID</summary>
    /// <remarks>For valid response try integer IDs with value <= 5 or > 10. Other values will generate exceptions.</remarks>
    /// <param name="orderId">ID of order that needs to be fetched</param>
    /// <returns>successful operation</returns>
    /// <exception cref="ApiException">
    /// Thrown when the request returns a non-success status code:
    /// <list type="table">
    /// <listheader>
    /// <term>Status</term>
    /// <description>Description</description>
    /// </listheader>
    /// <item>
    /// <term>400</term>
    /// <description>Invalid ID supplied</description>
    /// </item>
    /// <item>
    /// <term>404</term>
    /// <description>Order not found</description>
    /// </item>
    /// </list>
    /// </exception>
    [Headers("Accept: application/xml, application/json")]
    [Get("/store/order/{orderId}")]
    Task<Order> GetOrderById(long orderId);

    /// <summary>Delete purchase order by ID</summary>
    /// <remarks>For valid response try integer IDs with value < 1000. Anything above 1000 or nonintegers will generate API errors</remarks>
    /// <param name="orderId">ID of the order that needs to be deleted</param>
    /// <returns>A <see cref="Task"/> that completes when the request is finished.</returns>
    /// <exception cref="ApiException">
    /// Thrown when the request returns a non-success status code:
    /// <list type="table">
    /// <listheader>
    /// <term>Status</term>
    /// <description>Description</description>
    /// </listheader>
    /// <item>
    /// <term>400</term>
    /// <description>Invalid ID supplied</description>
    /// </item>
    /// <item>
    /// <term>404</term>
    /// <description>Order not found</description>
    /// </item>
    /// </list>
    /// </exception>
    [Delete("/store/order/{orderId}")]
    Task DeleteOrder(long orderId);

    /// <summary>Create user</summary>
    /// <remarks>This can only be done by the logged in user.</remarks>
    /// <param name="body">Created user object</param>
    /// <returns>successful operation</returns>
    /// <exception cref="ApiException">Thrown when the request returns a non-success status code.</exception>
    [Headers("Accept: application/json, application/xml")]
    [Post("/user")]
    Task CreateUser([Body] User body);

    /// <summary>Creates list of users with given input array</summary>
    /// <remarks>Creates list of users with given input array</remarks>
    /// <returns>Successful operation</returns>
    /// <exception cref="ApiException">Thrown when the request returns a non-success status code.</exception>
    [Headers("Accept: application/xml, application/json")]
    [Post("/user/createWithList")]
    Task<User> CreateUsersWithListInput([Body] IEnumerable<User> body);

    /// <summary>Logs user into the system</summary>
    /// <param name="queryParams">The dynamic querystring parameter wrapping all others.</param>
    /// <returns>successful operation</returns>
    /// <exception cref="ApiException">
    /// Thrown when the request returns a non-success status code:
    /// <list type="table">
    /// <listheader>
    /// <term>Status</term>
    /// <description>Description</description>
    /// </listheader>
    /// <item>
    /// <term>400</term>
    /// <description>Invalid username/password supplied</description>
    /// </item>
    /// </list>
    /// </exception>
    [Headers("Accept: application/xml, application/json")]
    [Get("/user/login")]
    Task<string> LoginUser([Query] LoginUserQueryParams queryParams);

    /// <summary>Logs out current logged in user session</summary>
    /// <returns>A <see cref="Task"/> that completes when the request is finished.</returns>
    /// <exception cref="ApiException">Thrown when the request returns a non-success status code.</exception>
    [Get("/user/logout")]
    Task LogoutUser();

    /// <summary>Get user by user name</summary>
    /// <param name="username">The name that needs to be fetched. Use user1 for testing.</param>
    /// <returns>successful operation</returns>
    /// <exception cref="ApiException">
    /// Thrown when the request returns a non-success status code:
    /// <list type="table">
    /// <listheader>
    /// <term>Status</term>
    /// <description>Description</description>
    /// </listheader>
    /// <item>
    /// <term>400</term>
    /// <description>Invalid username supplied</description>
    /// </item>
    /// <item>
    /// <term>404</term>
    /// <description>User not found</description>
    /// </item>
    /// </list>
    /// </exception>
    [Headers("Accept: application/xml, application/json")]
    [Get("/user/{username}")]
    Task<User> GetUserByName(string username);

    /// <summary>Update user</summary>
    /// <remarks>This can only be done by the logged in user.</remarks>
    /// <param name="username">name that needs to be updated</param>
    /// <param name="body">Update an existent user in the store</param>
    /// <returns>A <see cref="Task"/> that completes when the request is finished.</returns>
    /// <exception cref="ApiException">Thrown when the request returns a non-success status code.</exception>
    [Put("/user/{username}")]
    Task UpdateUser(string username, [Body] User body);

    /// <summary>Delete user</summary>
    /// <remarks>This can only be done by the logged in user.</remarks>
    /// <param name="username">The name that needs to be deleted</param>
    /// <returns>A <see cref="Task"/> that completes when the request is finished.</returns>
    /// <exception cref="ApiException">
    /// Thrown when the request returns a non-success status code:
    /// <list type="table">
    /// <listheader>
    /// <term>Status</term>
    /// <description>Description</description>
    /// </listheader>
    /// <item>
    /// <term>400</term>
    /// <description>Invalid username supplied</description>
    /// </item>
    /// <item>
    /// <term>404</term>
    /// <description>User not found</description>
    /// </item>
    /// </list>
    /// </exception>
    [Delete("/user/{username}")]
    Task DeleteUser(string username);

}    

public class UpdatePetWithFormQueryParams
{

    /// <summary>
    /// Name of pet that needs to be updated
    /// </summary>
    [Query] 
    public string Name { get; set; }

    /// <summary>
    /// Status of pet that needs to be updated
    /// </summary>
    [Query] 
    public string Status { get; set; }

}

public class LoginUserQueryParams
{

    /// <summary>
    /// The user name for login
    /// </summary>
    [Query] 
    public string Username { get; set; }

    /// <summary>
    /// The password for login in clear text
    /// </summary>
    [Query] 
    public string Password { get; set; }

}

RestService

Here's an example usage of the generated code above

using Refit;
using System;
using System.Threading.Tasks;

namespace Your.Namespace.Of.Choice.GeneratedCode;

internal class Program
{
    private static async Task Main(string[] args)
    {
        var client = RestService.For<ISwaggerPetstore>("https://petstore3.swagger.io/api/v3");
        var pet = await client.GetPetById(1);

        Console.WriteLine("## Using Task<T> as return type ##");
        Console.WriteLine($"Name: {pet.Name}");
        Console.WriteLine($"Category: {pet.Category.Name}");
        Console.WriteLine($"Status: {pet.Status}");
        Console.WriteLine();

        var client2 = RestService.For<WithApiResponse.ISwaggerPetstore>("https://petstore3.swagger.io/api/v3");
        var response = await client2.GetPetById(2);

        Console.WriteLine("## Using Task<IApiResponse<T>> as return type ##");
        Console.WriteLine($"HTTP Status Code: {response.StatusCode}");
        Console.WriteLine($"Name: {response.Content.Name}");
        Console.WriteLine($"Category: {response.Content.Category.Name}");
        Console.WriteLine($"Status: {response.Content.Status}");
    }
}

The RestService class generates an implementation of ISwaggerPetstore that uses HttpClient to make its calls.

The code above when run will output something like this:

## Using Task<T> as return type ##
Name: Gatitotototo
Category: Chaucito
Status: Sold

## Using Task<IApiResponse<T>> as return type ##
HTTP Status Code: OK
Name: Gatitotototo
Category: Chaucito
Status: Sold

ASP.NET Core and HttpClientFactory

Here's an example Minimal API with the Refit.HttpClientFactory library:

using Refit;
using Your.Namespace.Of.Choice.GeneratedCode;

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();
builder.Services
    .AddRefitClient<ISwaggerPetstore>()
    .ConfigureHttpClient(c => c.BaseAddress = new Uri("https://petstore3.swagger.io/api/v3"));

var app = builder.Build();
app.MapGet(
        "/pet/{id:long}",
        async (ISwaggerPetstore petstore, long id) =>
        {
            try
            {
                return Results.Ok(await petstore.GetPetById(id));
            }
            catch (Refit.ApiException e)
            {
                return Results.StatusCode((int)e.StatusCode);
            }
        })
    .WithName("GetPetById")
    .WithOpenApi();

app.UseHttpsRedirection();
app.UseSwaggerUI();
app.UseSwagger();
app.Run();

.NET Core supports registering the generated ISwaggerPetstore interface via HttpClientFactory

The following request to the API above

$ curl -X 'GET' 'https://localhost:5001/pet/1' -H 'accept: application/json'

Returns a response that looks something like this:

{
  "id": 1,
  "name": "Special_char_owner_!@#$^&()`.testing",
  "photoUrls": [
    "https://petstore3.swagger.io/resources/photos/623389095.jpg"
  ],
  "tags": [],
  "status": "Sold"
}

Dependency Injection

Refitter supports generating bootstrapping code that allows the user to conveniently configure all generated Refit interfaces by calling a single extension method to IServiceCollection.

This is enabled through the .refitter settings file like this:

{
  "openApiPath": "../OpenAPI/v3.0/petstore.json",
  "namespace": "Petstore",
  "dependencyInjectionSettings": {
    "baseUrl": "https://petstore3.swagger.io/api/v3",
    "httpMessageHandlers": [ "TelemetryDelegatingHandler" ],
    "transientErrorHandler": "Polly",
    "maxRetryCount": 3,
    "firstBackoffRetryInSeconds": 0.5
  }
}

which will generate an extension method to IServiceCollection called ConfigureRefitClients(). The generated extension method depends on Refit.HttpClientFactory library and looks like this:

public static IServiceCollection ConfigureRefitClients(
    this IServiceCollection services, 
    Action<IHttpClientBuilder>? builder = default, 
    RefitSettings? settings = default)
{
    var clientBuilderISwaggerPetstore = services
        .AddRefitClient<ISwaggerPetstore>(settings)
        .ConfigureHttpClient(c => c.BaseAddress = new Uri("https://petstore3.swagger.io/api/v3"))
        .AddHttpMessageHandler<TelemetryDelegatingHandler>();

    clientBuilderISwaggerPetstore
        .AddPolicyHandler(
            HttpPolicyExtensions
                .HandleTransientHttpError()
                .WaitAndRetryAsync(
                    Backoff.DecorrelatedJitterBackoffV2(
                        TimeSpan.FromSeconds(0.5),
                        3)));

    builder?.Invoke(clientBuilderISwaggerPetstore);

    return services;
}

This comes in handy especially when generating multiple interfaces, by tag or endpoint. For example, the following .refitter settings file

{
  "openApiPath": "../OpenAPI/v3.0/petstore.json",
  "namespace": "Petstore",
  "multipleInterfaces": "ByTag",
  "dependencyInjectionSettings": {
    "baseUrl": "https://petstore3.swagger.io/api/v3",
    "httpMessageHandlers": [ "TelemetryDelegatingHandler" ],
    "transientErrorHandler": "Polly",
    "maxRetryCount": 3,
    "firstBackoffRetryInSeconds": 0.5
  }
}

Will generate a single ConfigureRefitClients() extension methods that may contain dependency injection configuration code for multiple interfaces like this

public static IServiceCollection ConfigureRefitClients(
    this IServiceCollection services, 
    Action<IHttpClientBuilder>? builder = default, 
    RefitSettings? settings = default)
{
    var clientBuilderIPetApi = services
        .AddRefitClient<IPetApi>(settings)
        .ConfigureHttpClient(c => c.BaseAddress = new Uri("https://petstore3.swagger.io/api/v3"))
        .AddHttpMessageHandler<TelemetryDelegatingHandler>();

    clientBuilderIPetApi
        .AddPolicyHandler(
            HttpPolicyExtensions
                .HandleTransientHttpError()
                .WaitAndRetryAsync(
                    Backoff.DecorrelatedJitterBackoffV2(
                        TimeSpan.FromSeconds(0.5),
                        3)));

    builder?.Invoke(clientBuilderIPetApi);

    var clientBuilderIStoreApi = services
        .AddRefitClient<IStoreApi>(settings)
        .ConfigureHttpClient(c => c.BaseAddress = new Uri("https://petstore3.swagger.io/api/v3"))
        .AddHttpMessageHandler<TelemetryDelegatingHandler>();

    clientBuilderIStoreApi
        .AddPolicyHandler(
            HttpPolicyExtensions
                .HandleTransientHttpError()
                .WaitAndRetryAsync(
                    Backoff.DecorrelatedJitterBackoffV2(
                        TimeSpan.FromSeconds(0.5),
                        3)));

    builder?.Invoke(clientBuilderIStoreApi);

    var clientBuilderIUserApi = services
        .AddRefitClient<IUserApi>(settings)
        .ConfigureHttpClient(c => c.BaseAddress = new Uri("https://petstore3.swagger.io/api/v3"))
        .AddHttpMessageHandler<TelemetryDelegatingHandler>();

    clientBuilderIUserApi
        .AddPolicyHandler(
            HttpPolicyExtensions
                .HandleTransientHttpError()
                .WaitAndRetryAsync(
                    Backoff.DecorrelatedJitterBackoffV2(
                        TimeSpan.FromSeconds(0.5),
                        3)));

    builder?.Invoke(clientBuilderIUserApi);

    return services;
}

Personally, they I use Refitter is to generate an interface per endpoint, so when generating code for a large and complex API, I might have several interfaces.

Apizr

Apizr is a Refit client manager that provides a set of features to enhance requesting experience with resilience, caching, priority, mediation, mapping, logging, authentication, file transfer capabilities and many more...

Generating the interfaces

Refitter supports generating Apizr formatted Refit interfaces that can be managed then by Apizr (v6+).

You can enable Apizr formatted Refit interface generation either:

• With the --use-apizr command line argument
• By setting the apizrSettings section in the .refitter settings file

Note that --use-apizr uses default Apizr settings with withRequestOptions set to true as recommended, while the .refitter settings file allows you to configure it deeper.

In both cases, it will format the generated Refit interfaces to be Apizr ready by:

• Adding a final IApizrRequestOptions options parameter to all generated methods (if withRequestOptions is set to true)
• Providing cancellation tokens by Apizr request options instead of a dedicated parameter (if withRequestOptions is set to true)
• Using method overloads instead of optional parameters (note that setting useDynamicQuerystringParameters to true improve overloading experience)

From here, you're definitly free to use the formatted interface with Apizr by registering, configuring and using it following the Apizr documentation. But Refitter can go further by generating some helpers to make the configuration easier.

Generating the helpers

Refitter supports generating Apizr (v6+) bootstrapping code that allows the user to conveniently configure all generated Apizr formatted Refit interfaces by calling a single method. It could be either an extension method to IServiceCollection if DependencyInjectionSettings are set, or a static builder method if not.

Extended

To enable Apizr registration code generation for IServiceCollection, you need at least to set the withRegistrationHelper property to true and configure the DependencyInjectionSettings section in the .refitter settings file. This is what the .refitter settings file may look like, depending on you configuration:

{
  "openApiPath": "../OpenAPI/v3.0/petstore.json",
  "namespace": "Petstore",
  "useDynamicQuerystringParameters": true,
  "dependencyInjectionSettings": {
    "baseUrl": "https://petstore3.swagger.io/api/v3",
    "httpMessageHandlers": [ "MyDelegatingHandler" ],
    "transientErrorHandler": "HttpResilience",
    "maxRetryCount": 3,
    "firstBackoffRetryInSeconds": 0.5
  },
  "apizrSettings": {
    "withRequestOptions": true, // Recommended to include an Apizr request options parameter to Refit interface methods
    "withRegistrationHelper": true, // Mandatory to actually generate the Apizr registration extended method
    "withCacheProvider": "InMemory", // Optional, default is None
    "withPriority": true, // Optional, default is false
    "withMediation": true, // Optional, default is false
    "withOptionalMediation": true, // Optional, default is false
    "withMappingProvider": "AutoMapper", // Optional, default is None
    "withFileTransfer": true // Optional, default is false
  }
}

which will generate an extension method to IServiceCollection called ConfigurePetstoreApiApizrManager(). The generated extension method depends on Apizr.Extensions.Microsoft.DependencyInjection library and looks like this:

public static IServiceCollection ConfigurePetstoreApiApizrManager(
    this IServiceCollection services,
    Action<IApizrExtendedManagerOptionsBuilder>? optionsBuilder = null)
{
    optionsBuilder ??= _ => { }; // Default empty options if null
    optionsBuilder += options => options
        .WithBaseAddress("https://petstore3.swagger.io/api/v3", ApizrDuplicateStrategy.Ignore)
        .WithDelegatingHandler<MyDelegatingHandler>()
        .ConfigureHttpClientBuilder(builder => builder
            .AddStandardResilienceHandler(config =>
            {
                config.Retry = new HttpRetryStrategyOptions
                {
                    UseJitter = true,
                    MaxRetryAttempts = 3,
                    Delay = TimeSpan.FromSeconds(0.5)
                };
            }))
        .WithInMemoryCacheHandler()
        .WithAutoMapperMappingHandler()
        .WithPriority()
        .WithOptionalMediation()
        .WithFileTransferOptionalMediation();

    return services.AddApizrManagerFor<IPetstoreApi>(optionsBuilder);
}

This comes in handy especially when generating multiple interfaces, by tag or endpoint. For example, the following .refitter settings file

{
  "openApiPath": "../OpenAPI/v3.0/petstore.json",
  "namespace": "Petstore",
  "useDynamicQuerystringParameters": true,
  "multipleInterfaces": "ByTag",
  "naming": {    
    "useOpenApiTitle": false,
    "interfaceName": "Petstore"
  },
  "dependencyInjectionSettings": {
    "baseUrl": "https://petstore3.swagger.io/api/v3",
    "httpMessageHandlers": [ "MyDelegatingHandler" ],
    "transientErrorHandler": "HttpResilience",
    "maxRetryCount": 3,
    "firstBackoffRetryInSeconds": 0.5
  },
  "apizrSettings": {
    "withRequestOptions": true, // Recommended to include an Apizr request options parameter to Refit interface methods
    "withRegistrationHelper": true, // Mandatory to actually generate the Apizr registration extended method
    "withCacheProvider": "InMemory", // Optional, default is None
    "withPriority": true, // Optional, default is false
    "withMediation": true, // Optional, default is false
    "withOptionalMediation": true, // Optional, default is false
    "withMappingProvider": "AutoMapper", // Optional, default is None
    "withFileTransfer": true // Optional, default is false
  }
}

Will generate a single ConfigurePetstoreApizrManagers() extension method that may contain dependency injection configuration code for multiple interfaces like this

public static IServiceCollection ConfigurePetstoreApizrManagers(
    this IServiceCollection services,
    Action<IApizrExtendedCommonOptionsBuilder>? optionsBuilder = null)
{
    optionsBuilder ??= _ => { }; // Default empty options if null
    optionsBuilder += options => options
        .WithBaseAddress("https://petstore3.swagger.io/api/v3", ApizrDuplicateStrategy.Ignore)
        .WithDelegatingHandler<MyDelegatingHandler>()
        .ConfigureHttpClientBuilder(builder => builder
            .AddStandardResilienceHandler(config =>
            {
                config.Retry = new HttpRetryStrategyOptions
                {
                    UseJitter = true,
                    MaxRetryAttempts = 3,
                    Delay = TimeSpan.FromSeconds(0.5)
                };
            }))
        .WithInMemoryCacheHandler()
        .WithAutoMapperMappingHandler()
        .WithPriority()
        .WithOptionalMediation()
        .WithFileTransferOptionalMediation();

    return services.AddApizr(
        registry => registry
            .AddManagerFor<IPetApi>()
            .AddManagerFor<IStoreApi>()
            .AddManagerFor<IUserApi>(),
        optionsBuilder);

}

Here, IPetApi, IStoreApi and IUserApi are the generated interfaces which share the same common configuration defined from the .refitter file.

Static

To enable Apizr static builder code generation, you need at least to set the withRegistrationHelper property to true and leave the DependencyInjectionSettings section to null in the .refitter settings file. This is what the .refitter settings file may look like, depending on you configuration:

{
  "openApiPath": "../OpenAPI/v3.0/petstore.json",
  "namespace": "Petstore",
  "useDynamicQuerystringParameters": true,
  "apizrSettings": {
    "withRequestOptions": true, // Recommended to include an Apizr request options parameter to Refit interface methods
    "withRegistrationHelper": true, // Mandatory to actually generate the Apizr registration extended method
    "withCacheProvider": "Akavache", // Optional, default is None
    "withPriority": true, // Optional, default is false
    "withMappingProvider": "AutoMapper", // Optional, default is None
    "withFileTransfer": true // Optional, default is false
  }
}

which will generate a static builder method called BuildPetstore30ApizrManager(). The generated builder method depends on Apizr library and looks like this:

public static IApizrManager<ISwaggerPetstoreOpenAPI30> BuildPetstore30ApizrManager(Action<IApizrManagerOptionsBuilder> optionsBuilder)
{
    optionsBuilder ??= _ => { }; // Default empty options if null
    optionsBuilder += options => options
        .WithAkavacheCacheHandler()
        .WithAutoMapperMappingHandler(new MapperConfiguration(config => { /* YOUR_MAPPINGS_HERE */ }))
        .WithPriority();

    return ApizrBuilder.Current.CreateManagerFor<ISwaggerPetstoreOpenAPI30>(optionsBuilder);  
}

This comes in handy especially when generating multiple interfaces, by tag or endpoint. For example, the following .refitter settings file

{
  "openApiPath": "../OpenAPI/v3.0/petstore.json",
  "namespace": "Petstore",
  "useDynamicQuerystringParameters": true,
  "multipleInterfaces": "ByTag",
  "naming": {    
    "useOpenApiTitle": false,
    "interfaceName": "Petstore"
  },
  "dependencyInjectionSettings": {
    "baseUrl": "https://petstore3.swagger.io/api/v3",
    "httpMessageHandlers": [ "MyDelegatingHandler" ],
    "transientErrorHandler": "HttpResilience",
    "maxRetryCount": 3,
    "firstBackoffRetryInSeconds": 0.5
  },
  "apizrSettings": {
    "withRequestOptions": true, // Recommended to include an Apizr request options parameter to Refit interface methods
    "withRegistrationHelper": true, // Mandatory to actually generate the Apizr registration extended method
    "withCacheProvider": "InMemory", // Optional, default is None
    "withPriority": true, // Optional, default is false
    "withMediation": true, // Optional, default is false
    "withOptionalMediation": true, // Optional, default is false
    "withMappingProvider": "AutoMapper", // Optional, default is None
    "withFileTransfer": true // Optional, default is false
  }
}

Will generate a single BuildPetstoreApizrManagers() builder method that may contain configuration code for multiple interfaces like this

public static IApizrRegistry BuildPetstoreApizrManagers(Action<IApizrCommonOptionsBuilder> optionsBuilder)
{
    optionsBuilder ??= _ => { }; // Default empty options if null
    optionsBuilder += options => options
        .WithAkavacheCacheHandler()
        .WithAutoMapperMappingHandler(new MapperConfiguration(config => { /* YOUR_MAPPINGS_HERE */ }))
        .WithPriority();

    return ApizrBuilder.Current.CreateRegistry(
        registry => registry
            .AddManagerFor<IPetApi>()
            .AddManagerFor<IStoreApi>()
            .AddManagerFor<IUserApi>(),
        optionsBuilder);
}

Here, IPetApi, IStoreApi and IUserApi are the generated interfaces which share the same common configuration defined from the .refitter file.

Customizing the configuration

You may want to adjust apis configuration, for example, to add a custom header to requests. This can be done using the Action<TApizrOptionsBuilder> parameter while calling the generated method. To know how to make Apizr fit your needs, please refer to the Apizr documentation.

Using the managers

Once you called the generated method, you will get an IApizrManager<T> instance that you can use to make requests to the API. Here's an example of how to use it:

var result = await petstoreManager.ExecuteAsync((api, opt) => api.GetPetById(1, opt), 
    options => options // Whatever final request options you want to apply
        .WithPriority(Priority.Background)
        .WithHeaders(["HeaderKey1: HeaderValue1"])
        .WithRequestTimeout("00:00:10")
        .WithCancellation(cts.Token));

Please head to the Apizr documentation to get more.

System requirements

.NET 8.0

Contributors

Philip Cox 💻	Cameron MacFarland 💻	kgame 💻	Thomas Pettersen / Yrki 💻	Artem 🐛	m7clarke 🐛	kirides 🐛 💻
guillaumeserale 💻 🐛	Dennis Brentjes 💻 🤔	Damian Hickey 🐛	richardhu-lmg 🐛	brease-colin 🐛	angelofb 💻	Dim Nogro 💻
yadanilov19 🤔 💻	Daniel Powell 🐛	Ekkeir 📖 🐛	Waylon Martinez 🐛	vkmadupa 🐛	Noblix 💻 🤔	Attila Hajdrik 🤔
bielik01 🐛 🤔	naaeef 🤔	Alireza Habibi 🐛	Jeff Parker, PE 🐛	jods 🤔 🐛	Edimarquez Medeiros 💻	safakkesikci 🐛
folbrecht 🐛	mortenlaursen 💻	manuel-fernandez-rodriguez 🐛	Eli Yammine 🐛	kami-poi 🤔	Xeevis 🐛	DJ4ddi 💻 🤔
direncancatalkaya 💻	Robert Palmqvist 🤔 💻	Tim M 📖	janfolbrecht 🤔 💻	Nick Seguin 💻	David Brink 🐛 💻	Stu Wilson 🤔 💻
sharpzilla 🤔	Tatu 🐛	Jérémy BRUN-PICARD 🤔 💻 📖	Ed Barnard 🤔	bastien.noel 🐛	Meikel Philipp 🤔	Berk Selvi 🤔 💻
Joshua Ozeri 🐛	Ryan Heath 🤔 💻	Brian Brunner 🤔	Frank Samiec 💻	Fabio Loreggian 🐛	geometrikal 🐛	Shubin Pavel 💻
Wiebe Tijsma 🤔

#

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