public class ClassA<TUid>
{
    public TUid? Uid { get; set; }
}

public class ClassB : ClassA<Guid>
{
    public void Test()
    {
        ClassB dto = new ClassB();
        dto.Uid = null;
    }
}

C# compiler doesn’t accept this C# code at the line: dto.Uid = null saying that

Cannot convert null to ‘Guid’ because it is a non-nullable value type

Isn’t generic type TUid in ClassA substituted with Guid in ClassB so it should result in Guid? like this?

public Guid? Uid { get; set; }

If I declare ClassA as non-generic

public class ClassA
{
    public TUid? Uid { get; set; }
}

or pass generic parameter as Guid?

public class ClassB : ClassA<Guid?>

then dto.Uid = null doesn’t cause any problem.

What is it about the parameter type inference rules that confuses the compiler in the first example?