Is it possible to implement a COM interface with a .NET generics class?

8
votes

I have the following interface which I'm trying to make COM-visible. When I try to generate the type-library it doesn't like the fact that my implementation class derives from a generic-class.

Is it possible to use a generic class as a COM implementation class? (I know I could write a non-generic wrapper and export that to COM, but this adds another layer that I'd rather do without.)

[ComVisible(true)]
public interface IMyClass
{
   ...
}

[ComVisible(true), ComDefaultInterface(typeof(IMyClass))]
[ClassInterface(ClassInterfaceType.None)]
public class MyClass : BaseClass<IMyClass>, IMyClass
{
   ...
}

Error message:

Warning: Type library exporter encountered a type that derives 
from a generic class and is not marked as 
[ClassInterface(ClassInterfaceType.None)]. Class interfaces cannot
be exposed for such types. Consider marking the type with 
[ClassInterface(ClassInterfaceType.None)] 
and exposing an explicit interface as the default interface to 
COM using the ComDefaultInterface attribute.
1
.netgenericscomcomvisible

1 Answers

6
votes

Generic types and types that derive from a generic type cannot be exported. Set ComVisible(false) on your MyClass type. You'll need to either create a non-generic class implementation or use the interface only.