How to pass a COM object as an IntPtr to a P/Invoke method?
See the question and my original answer on StackOverflowYou want to use the Marshal.GetIUnknownForObject Method.
Simon Mourier's blog (1807 answers on StackOverflow) about Microsoft technologies C#, C/C++, .NET, WinRT, WinUI3, AOT, P/Invoke, COM, Interop, DirectX, Direct2D, Windows, ...