ASP.NET Core IQueryable Extensions

Lightweight API that construct custom IQueryable LINQ Extensions to help you filter, sort and paginate your objects from a custom Class and expose it as GET parameter.

Table of Contents

• ASP.NET Core IQueryable Extensions
  • Table of Contents
• How
• Sort
• Paging
• All in One
• Criterias for filtering
• Different database fields name
• Or Operator
• Why
• License

How

You should install AspNetCore.IQueryable.Extensions with NuGet:

    Install-Package AspNetCore.IQueryable.Extensions

Or via the .NET Core command line interface:

    dotnet add package AspNetCore.IQueryable.Extensions

Create a class with filtering properties:

public class UserSearch
{
    public string Username { get; set; }

    [QueryOperator(Operator = WhereOperator.GreaterThan)]
    public DateTime? Birthday { get; set; }

    [QueryOperator(Operator = WhereOperator.Contains, HasName = "Firstname")]
    public string Name { get; set; }
}

Expose this class as GET in your API and use it to Filter your collection:

[HttpGet("")]
public async Task<ActionResult<IEnumerable<User>>> Get([FromQuery] UserSearch search)
{
    var result = await context.Users.AsQueryable().Filter(search).ToListAsync();

    return Ok(result);
}

Done!

You can send a request to you API like this: https://www.myapi.com/users?username=bhdebrito@gmail.com&name=bruno

The component will construct a IQueryable. If you are using an ORM like EF Core it construct a SQL query based in IQueryable, improving performance.

Sort

A comma separetd fields. E.g username,birthday,-firstname

-(minus) for descending +(plus) or nothing for ascending

public class UserSearch
{
    public string Username { get; set; }

    public string SortBy { get; set; }
}

[HttpGet("")]
public async Task<ActionResult<IEnumerable<User>>> Get([FromQuery] UserSearch search)
{
    var result = await context.Users.AsQueryable().Filter(search).Sort(search.SortBy).ToListAsync();

    return Ok(result);
}

Example GET: https://www.myapi.com/users?username=bruno&sortby=username,-birtday

Paging

A exclusive extension for paging

public class UserSearch
{
    public string Username { get; set; }

    [QueryOperator(Max = 100)]
    public int Limit { get; set; } = 10;

    public int Offset { get; set; } = 0;
}

Limit is the total results in response. Offset is how many rows to Skip. Optionally you can set the Max attribute to restrict the max items of pagination.

[HttpGet("")]
public async Task<ActionResult<IEnumerable<User>>> Get([FromQuery] UserSearch search)
{
    var result = await context.Users.AsQueryable().Filter(search).Paging(search.Limit, search.Offset).ToListAsync();

    return Ok(result);
}

Example GET: https://www.myapi.com/users?username=bruno&limit=10&offset=20

All in One

Create a search class like this

public class UserSearch : IQuerySort, IQueryPaging
{
    public string Username { get; set; }

    [QueryOperator(Operator = WhereOperator.GreaterThan)]
    public DateTime? Birthday { get; set; }

    [QueryOperator(Operator = WhereOperator.Contains, HasName = "Firstname")]
    public string Name { get; set; }

    public int Offset { get; set; }
    public int Limit { get; set; } = 10;
    public string Sort { get; set; }
}

Call Apply method, instead calling each one with custom parameters.

[HttpGet("")]
public async Task<ActionResult<IEnumerable<User>>> Get([FromQuery] UserSearch search)
{
    var result = await context.Users.AsQueryable().Apply(search).ToListAsync();

    return Ok(result);
}

IQuerySort and IQueryPaging give the ability for method Apply use Sort and Pagination. If don't wanna sort, just use pagination remove IQuerySort Interface from Class.

Criterias for filtering

When creating a Search class, you can define criterias by decorating your properties:

public class CustomUserSearch
{
    [QueryOperator(Operator = WhereOperator.Equals, UseNot = true)]
    public string Category { get; set; }

    [QueryOperator(Operator = WhereOperator.GreaterThanOrEqualTo)]
    public int OlderThan { get; set; }

    [QueryOperator(Operator = WhereOperator.StartsWith, CaseSensitive = true)]
    public string Username { get; set; }

    [QueryOperator(Operator = WhereOperator.GreaterThan)]
    public DateTime? Birthday { get; set; }

    [QueryOperator(Operator = WhereOperator.Contains)]
    public string Name { get; set; }
}

Different database fields name

You can specify different property name to hide you properties original fields

public class CustomUserSearch
{
    [QueryOperator(Operator = WhereOperator.Equals, UseNot = true, HasName = "Privilege")]
    public string Category { get; set; }

    [QueryOperator(Operator = WhereOperator.GreaterThanOrEqualTo)]
    public int OlderThan { get; set; }

    [QueryOperator(Operator = WhereOperator.StartsWith, CaseSensitive = true, HasName = "Username")]
    public string Email { get; set; }
}

Or Operator

You can use Or operator for your queries.

public class CustomUserSearch
{
    [QueryOperator(Operator = WhereOperator.Equals, UseOr = true]
    public string Category { get; set; }

    [QueryOperator(Operator = WhereOperator.GreaterThanOrEqualTo)]
    public int OlderThan { get; set; }

    [QueryOperator(Operator = WhereOperator.StartsWith, CaseSensitive = true, HasName = "Username")]
    public string Email { get; set; }
}

Take care, Or replace all "AND" at query.

Why

RESTFul api's are hard to create. See the example get:

https://www.myapi.com/users?name=bruno&age_lessthan=30&sortby=name,-age&limit=20&offset=20

How many code you need to perform such search? A custom filter for each Field, maybe a for and a switch for each sortby and after all apply pagination. How many resources your api have?

This lightweight API create a custom IQueryable based in Querystring to help your ORM or LINQ to filter data.

License

AspNet.Core.IQueryable.Extensions is Open Source software and is released under the MIT license. This license allow the use of AspNet.Core.IQueryable.Extensions in free and commercial applications and libraries without restrictions.