NullReferenceException in SqlServerAnnotationCodeGenerator when scaffolding columns with named default constraints and CLR default values

[collinbarrett]

Bug description

When scaffolding a database with dotnet ef dbcontext scaffold, a NullReferenceException occurs in SqlServerAnnotationCodeGenerator.GenerateFluentApiCalls for columns that have both:

• A named default constraint (e.g., DF_TableName_ColumnName)
• A default value equal to the CLR default (e.g., DEFAULT ((0)) for int)

This appears related to PR #36067 (named default constraint support). Issue #36567 claims to fix this scenario and was tagged for the 10.0.0 milestone, but the bug reproduces in the released 10.0.0 stable version.

Your code

Create a table with a named default constraint where the default value equals the CLR default:

CREATE TABLE TestTable (
    Id INT NOT NULL PRIMARY KEY,
    Value INT NOT NULL CONSTRAINT DF_TestTable_Value DEFAULT ((0))
);

Scaffold the database:

dotnet ef dbcontext scaffold "Server=myserver;Database=mydb;..." Microsoft.EntityFrameworkCore.SqlServer --output-dir Models --context TestContext --force

Result: Scaffolding fails with NullReferenceException

Possible root cause: In SqlServerAnnotationCodeGenerator.GenerateFluentApiCalls (v10.0.0, line 282):

1. Base scaffolder removes DefaultValue annotation because 0 equals CLR default for int
2. Then attempts to remove DefaultValue again (no-op since already removed)
3. Then accesses defaultValueAnnotation.Value to generate fluent API code
4. defaultValueAnnotation is null → NullReferenceException

This is a different bug than #36567, which crashed when REMOVING the constraint name annotation.
This bug crashes when ACCESSING the default value annotation to generate code.

Why This is a Regression

Issue #36567 was marked as fixed in PR #36576 for the 10.0.0 milestone, but the fix only addressed one scenario.

The fix in #36576 didn't account for the case where BOTH conditions are true:

• Named constraint exists (introduced by PR Fix to #11502 - Allow to specify constraint name for default values #36067)
• Default value equals CLR default (removed by base scaffolder before SQL Server provider runs)

This causes the null reference when the SQL Server-specific code assumes the DefaultValue annotation still exists.

Stack traces

System.NullReferenceException: Object reference not set to an instance of an object.
   at Microsoft.EntityFrameworkCore.SqlServer.Design.Internal.SqlServerAnnotationCodeGenerator.GenerateFluentApiCalls(IProperty property, IDictionary`2 annotations)
   at Microsoft.EntityFrameworkCore.Design.IAnnotationCodeGenerator.GenerateFluentApiCallsInternal(IAnnotatable annotatable, IDictionary`2 annotations)
   at Microsoft.EntityFrameworkCore.ScaffoldingModelExtensions.GenerateAnnotations(IAnnotatable annotatable, Dictionary`2 annotations, IAnnotationCodeGenerator annotationCodeGenerator, Boolean isHandledByDataAnnotations)
   at Microsoft.EntityFrameworkCore.ScaffoldingModelExtensions.GetFluentApiCalls(IProperty property, IAnnotationCodeGenerator annotationCodeGenerator)
   at Microsoft.VisualStudio.TextTemplating.GeneratedTextTransformation.TransformText()

Verbose output

Microsoft.EntityFrameworkCore.Design.OperationException: Processing 'DbContext.t4' failed.
   at Microsoft.EntityFrameworkCore.Scaffolding.Internal.TextTemplatingModelGenerator.HandleErrors(TextTemplatingHost host)
   at Microsoft.EntityFrameworkCore.Scaffolding.Internal.TextTemplatingModelGenerator.GenerateModel(IModel model, ModelCodeGenerationOptions options)
   at Microsoft.EntityFrameworkCore.Design.Internal.DatabaseOperations.ScaffoldContext(...)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.ScaffoldContextImpl(...)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.ScaffoldContext.<>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)
Processing 'DbContext.t4' failed.

EF Core version

10.0.0

Database provider

Microsoft.EntityFrameworkCore.SqlServer 10.0.0
Microsoft.EntityFrameworkCore.Design 10.0.0

Target framework

.NET 10.0

Operating system

Windows 11

IDE

Command line (dotnet ef)

[SSchwarzlose-gt]

I have a similar problem for columns that have:

• A Constraint Name
• An Annotation

An operation was scaffolded that may result in the loss of data. Please review the migration for accuracy.
System.NullReferenceException: Object reference not set to an instance of an object.
   at Microsoft.EntityFrameworkCore.SqlServer.Design.Internal.SqlServerAnnotationCodeGenerator.GenerateFluentApiCalls(IProperty property, IDictionary`2 annotations)
   at Microsoft.EntityFrameworkCore.Design.IAnnotationCodeGenerator.GenerateFluentApiCallsInternal(IAnnotatable annotatable, IDictionary`2 annotations)
   at Microsoft.EntityFrameworkCore.Design.AnnotationCodeGenerator.GenerateFluentApiCalls(IAnnotatable annotatable, IDictionary`2 annotations)
   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.GeneratePropertyAnnotations(String propertyBuilderName, IProperty property, IndentedStringBuilder stringBuilder)
   at Microsoft.EntityFrameworkCore.Migrations.Design.CSharpSnapshotGenerator.GenerateProperty(String entityTypeBuilderName, IProperty property, IndentedStringBuilder stringBuilder)
   at Microsoft.EntityFrameworkCore.Migrations.Design.CSharpSnapshotGenerator.GenerateProperties(String entityTypeBuilderName, IEnumerable`1 properties, IndentedStringBuilder stringBuilder)
   at Microsoft.EntityFrameworkCore.Migrations.Design.CSharpSnapshotGenerator.GenerateEntityType(String builderName, IEntityType entityType, IndentedStringBuilder stringBuilder)
   at Microsoft.EntityFrameworkCore.Migrations.Design.CSharpSnapshotGenerator.GenerateEntityTypes(String modelBuilderName, IEnumerable`1 entityTypes, IndentedStringBuilder stringBuilder)
   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)