I want to be able to derive from a class internally, but disallow class in other assemblies to derive from the class

Hej

I have the following setup:

Assembly 1

public abstract class XX<T> : XX where T: YY { }
public abstract class XX {}

Assembly 2

public class ZZ : YY {}
public class ZZFriend : XX<ZZ> {}

I use this feature in reflection when in YY:

public class YY {
  public Type FindFriend {
    return GetType().Assembly.GetTypes().FirstOrDefault(
      t => t.BaseType != null &&
      t.BaseType.IsGenericType &&
      typeof(XX).IsAssignableFrom(t) &&
      t.BaseType.GetGenericArguments().FirstOrDefault() == GetType());
  }
}

I would like do disallow inheritance of the non generic class XX like:

public class ZZFriend: XX {}

Alternatively, I need a method like (that can be used in the reflection in YY.FindFrind()):

public Type F(Type t) {
  return GetTypeThatIsGeneric(XX, Type genericTypeParameter);
}

That can be used in YY as:

Typeof(XX<ZZ) == F(typeof(GetType())

Hope that makes sense...

Thanks in advance

Søren Rokkedal