When extending a COM class in unmanaged C++ where the original class has private interfaces, one way to do this is through the concept of blind aggregation. The idea is that any interface not explicitly implemented on the outer aggregating class is 'blindly' forwarded to the inner aggregated class.
Now .NET as far as I can figure out does not support COM aggregation natively. A somewhat tedious workaround is to create a .NET class where you implement all the required COM interfaces directly on the .NET class and simply forward to an instance of the actual COM class for any methods you don't want to override.
The problem I have is when the original COM object has one or more private interfaces, i.e. undocumented interfaces that are nonetheless used by some consumers of the original class. Using blind aggregation in unmanaged C++ this is a non-issue as the calls to the private interfaces are automatically forwarded to the original class, however I can't find any way of doing the same thing in .NET. Are there any other ways of accomplishing this with .NET?