使用COM接口时System.InvalidCastException

Question

I wrote a atl COM dll, dual. And used one of its intreace X in a C# GUI proj. when call XF(), I got an System.InvalidCastException, can not cast namespace.XClass to namespace.IX, QueryInterface failed: BADTYPE. The call was in my own thread.

If i move the code to the GUI thread, it works just fine.

Please help me with that. Thanks a lot.

Answer 1

COM对象通常是STA，这意味着它们只能由创建它们的线程使用

Answer 2

COM requires a proxy/stub to marshal the call from the thread to the thread that created the object. QI will fail if it cannot find it in the HKCR\\Interface registry key.