COM interop object throws InvalidCastException in one project but not in other

Question

I have a COM object I imported in my test C# solution. Everything works fine and continues to do so.

Then I imported the same COM object in my actual solution and as

Answer 1

The difference was in threading. The winform thread executed the code from the main thread, whereas the asp.net didn't. It was solved by explicitly running the COM in a STAThread.