System.InvalidOperationException: Cannot scaffold C# literals of type 'System.Reflection.NullabilityInfoContext' during migration

[Asyvix]

When attempting to create a new migration in my project using Entity Framework Core, I encountered the following error:

   at Microsoft.EntityFrameworkCore.Design.Internal.CSharpHelper.UnknownLiteral(Object value)
   at Microsoft.EntityFrameworkCore.Design.Internal.CSharpHelper.<Fragment>g__AppendMethodCall|57_0(IMethodCallCodeFragment current, <>c__DisplayClass57_0&)
   at Microsoft.EntityFrameworkCore.Design.Internal.CSharpHelper.Fragment(IMethodCallCodeFragment fragment, Int32 indent)
   at Microsoft.EntityFrameworkCore.Migrations.Design.CSharpSnapshotGenerator.GenerateAnnotations(String builderName, IAnnotatable annotatable, IndentedStringBuilder stringBuilder, Dictionary`2 annotations, Boolean inChainedCall, Boolean leadingNewline, MethodInfo hasAnnotationMethodInfo)
   at Microsoft.EntityFrameworkCore.Migrations.Design.CSharpSnapshotGenerator.Generate(String modelBuilderName, IModel model, IndentedStringBuilder stringBuilder)
   at Microsoft.EntityFrameworkCore.Migrations.Design.CSharpMigrationsGenerator.GenerateMetadata(String migrationNamespace, Type contextType, String migrationName, String migrationId, IModel targetModel)
   at Microsoft.EntityFrameworkCore.Migrations.Design.MigrationsScaffolder.ScaffoldMigration(String migrationName, String rootNamespace, String subNamespace, String language, Boolean dryRun)
   at Microsoft.EntityFrameworkCore.Design.Internal.MigrationsOperations.AddMigration(String name, String outputDir, String contextType, String namespace, Boolean dryRun)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigrationImpl(String name, String outputDir, String contextType, String namespace, Boolean dryRun)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigration.<>c__DisplayClass0_0.<.ctor>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.<>c__DisplayClass3_0`1.<Execute>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)
Cannot scaffold C# literals of type 'System.Reflection.NullabilityInfoContext'. The provider should implement CoreTypeMapping.GenerateCodeLiteral to support using it at design time.

Expected Behavior: The migration should scaffold without errors, as it did in .NET 8.

Actual Behavior: The process fails with the above error after upgrading to .NET 9.

Additional Context: the migration process worked without issues in .NET 8 but fails in .NET 9.

I attempted to use the --verbose flag to obtain more detailed logs, but it did not provide additional meaningful information.

[roji]

Duplicate of https://github.com/dotnet/efcore/issues/34996

[Asyvix]

i know that issue. but im not use private backing fields. All I'm doing is using Dictioanry with Jsonb.

[roji]

@ajcvickers am not sure, does this issue look like it has the same root cause as https://github.com/dotnet/efcore/issues/34996?

[Asyvix]

The cause of the issue is still unknown, and I am struggling to resolve it. Since the model is quite large, thoroughly reviewing it may take some time. In EF Core with PostgreSQL, we always use jsonb for necessary properties, and we generally avoid using arrays. Instead, relationships between models are mapped using foreign keys (FK).

Regardless of whether any issues are identified, I will add new comments here after completing my review.

[Asyvix]

The issue has been resolved.

Root Cause Analysis

The issue was not related to the Property in the model but rather to the Field. Below is the comparison of the code that highlights the problem:

Previous Code:

public string[] SearchKeys = new string[] { };

Updated Code:

public string[] SearchKeys { get; set; } = new string[] { };

This subtle difference caused the issue. While it seems trivial, it had a significant impact on the behavior of the Entity Framework Core (EF Core) and the Npgsql provider.

Questions and Observations

1. Should a field, as opposed to a property, affect the migration process?

   • Ideally, fields should not affect the migration process unless explicitly mapped. Properties are the primary mechanism EF Core uses to define entity mappings.

2. Should fields, including backing fields or fields not directly connected to a property, be involved in entity conversions?

   • Fields not explicitly mapped should be ignored. However, the behavior can vary depending on configurations, conventions, or provider-specific implementation details. In this case, the use of an indexed field might have inadvertently caused it to be treated as part of the model.

Key Takeaways

• The relationship between fields and entities must be explicit. Unintended behavior can occur when fields are assumed to be ignored but are implicitly included in the model.
• Backing fields can be useful for certain advanced scenarios but should be configured carefully to avoid ambiguity.
• The use of indexed fields (or indexing in general) can introduce unexpected side effects if EF Core interprets them as part of the model mapping.

Reflection

Looking back, this issue emphasizes the importance of understanding how EF Core and its providers handle field and property mappings. While it feels like a minor oversight, it highlights the need for clarity in defining entity relationships and behaviors.

If only we could converse with our past selves to address these quirks earlier, such avoidable frustrations could have been minimized.

[Asyvix]

Additional information: If there is no index on SearchKeys, the issue does not occur.

Ultimately, the problem arises when an index includes SearchKeys, but SearchKeys is defined as a field rather than a property.