dotnet/efcore · error · InvalidOperationException

The property ' . ' has a value generator configured. Use '…

Error message

The property '{entityType}.{property}' has a value generator configured. Use '{method}' to configure the value generator factory type.

What it means

Thrown by CSharpRuntimeModelCodeGenerator when a property has a value generator instance configured (GetValueGeneratorFactory() is non-null) but no ValueGeneratorFactoryType annotation. Compiled models can only persist a factory type (so it can be reconstructed), not an arbitrary generator instance, so an instance-only configuration is refused; the message directs you to use HasValueGeneratorFactory instead.

Solutions

Switch from HasValueGenerator<TInstance>() to HasValueGeneratorFactory<TFactory>() so the compiled model can store the type.
Provide a ValueGenerator factory type that the compiled model can serialize.
If an instance is truly required, accept that the compiled model cannot encode it and configure it at runtime.

Example fix

// before
modelBuilder.Entity<E>().Property(p => p.Id).HasValueGenerator<MyGenerator>();
// after
modelBuilder.Entity<E>().Property(p => p.Id).HasValueGeneratorFactory<MyGeneratorFactory>();

Defensive patterns

Strategy: validation

Validate before calling

// Detect instance-based value generators before compiled-model generation
foreach (var p in model.GetEntityTypes().SelectMany(e => e.GetProperties()))
{
    var factoryType = (Type?)p[CoreAnnotationNames.ValueGeneratorFactoryType];
    if (factoryType is null && p.GetValueGeneratorFactory() is not null)
        Console.WriteLine($"{p.DeclaringType}.{p.Name} uses an instance generator; switch to HasValueGeneratorFactory.");
}

Try / catch

try { Optimize(); }
catch (InvalidOperationException ex) when (ex.Message.Contains("value generator"))
{ /* switch to HasValueGeneratorFactory<TFactory> then regenerate */ }

Prevention

Use HasValueGeneratorFactory<TFactory> instead of HasValueGenerator<TInstance> when targeting compiled models.
Audit value-generator configuration before running optimize.
Document that compiled models can only serialize generator factory types, not instances.

When it happens

Trigger: Configuring a property with HasValueGenerator(...) (an instance) rather than HasValueGeneratorFactory(...) (a type), then generating a compiled model.

Common situations: Custom value generators registered as instances; migrating value-generator configuration to the compiled-model workflow.

Related errors

AI-assisted analysis of dotnet/efcore@3a2006ef56 (2026-08-11). Data as JSON: /api/errors/6d30b499347db8fb. Report an issue: GitHub.

Appendix: source

Thrown at src/EFCore.Design/Scaffolding/Internal/CSharpRuntimeModelCodeGenerator.cs:1088

                    .Append(_code.UnknownLiteral(providerValue))
                    .AppendLine(");")
                    .AppendLine();
            }
        }
    }

    private void Create(
        IProperty property,
        Dictionary<MemberInfo, QualifiedName>? memberAccessReplacements,
        CSharpRuntimeAnnotationCodeGeneratorParameters parameters)
    {
        var variableName = _code.Identifier(property.Name, property, parameters.ScopeObjects, capitalize: false);

        var valueGeneratorFactoryType = (Type?)property[CoreAnnotationNames.ValueGeneratorFactoryType];
        if (valueGeneratorFactoryType == null
            && property.GetValueGeneratorFactory() != null)
        {
            throw new InvalidOperationException(
                DesignStrings.CompiledModelValueGenerator(
                    property.DeclaringType.ShortName(), property.Name, nameof(PropertyBuilder.HasValueGeneratorFactory)));
        }

        var mainBuilder = parameters.MainBuilder;
        mainBuilder
            .Append("var ").Append(variableName).Append(" = ").Append(parameters.TargetName).AppendLine(".AddProperty(")
            .IncrementIndent()
            .Append(_code.Literal(property.Name));

        GeneratePropertyBaseParameters(property, parameters);

        if (property.IsNullable)
        {
            mainBuilder.AppendLine(",")
                .Append("nullable: ")
                .Append(_code.Literal(true));
        }

View on GitHub (pinned to 3a2006ef56)