Inheriting from .NET classes

Hi, everybody.

I am trying to inherit a non visual custom object from a .NET class named  "System.ServiceModel.DuplexClientBase<T>", but I got this error below:

I have downloaded the WPFToolkit, just in case, but it didn't work as well.

I've noticed I can inherit from most of the  available .NET Classes, except the ones with the <T> parameter

I've read in the Powerbuilder .NET Features Guide the following information:

I guess it doesn't work properly, as I am  not  able to even create my nonvisual object in first place.

Have you ever faced something like that in your projects?

Thanks, guys