Diagnostics

The package includes an analyzer that reports the declarations that the generator cannot handle. When it reports an error on a type, no code is generated for that type, so the errors that follow (a missing FromInt32 or Value) disappear once the first one is fixed.

MFSTID0001: Not supported type

The underlying type of the attribute is not one of the supported types, for instance [StronglyTypedId<TimeSpan>]. The types that are only supported on some frameworks (Int128, UInt128, Half) and ObjectId (which needs a reference to MongoDB.Bson) are reported when they are not available.

Fix: use a supported type. To wrap a value of another type, write the type by hand, or store a supported representation of the value (a long number of ticks instead of a TimeSpan).

MFSTID0002: Guid generation strategy is not supported by the target framework

GuidGenerationStrategy = GuidGenerationStrategy.Version7 is set, on a type or in StronglyTypedIdDefaults, but the target framework has no Guid.CreateVersion7(), which appeared in .NET 9.

Fix: target .NET 9 or later, or use Version4 or None. In a project with several target frameworks, the error is reported for the older ones.

MFSTID0003: Guid generation strategy is only applicable to Guid

GuidGenerationStrategy is set on an ID that does not wrap a Guid. The option has no effect: only Guid IDs have a New() method.

Fix: remove the option, or change the underlying type to Guid. A GuidGenerationStrategy set in StronglyTypedIdDefaults is not reported: it applies to the Guid IDs of the assembly only.

MFSTID0004: Generic types are not supported

The ID is generic (ProjectId<T>), or nested in a generic type. The converters are registered by attributes on the ID, and an attribute argument cannot use a type parameter (CS0416), so the generator cannot register them.

Fix: declare the ID as a non-generic type, outside of generic types.