Understanding COM threading model(Apartment)
I have found very useful articles for understanding COM threading model about Apartment. If you want to understand COM Apartment model, the following articles will help you a lot.
Understanding COM Apartments, Part I - CodeGuru
Understanding COM Apartments, Part II - CodeGuru
Understanding The COM Single-Threaded Apartment Part 1 - CodeProject
Understanding The COM Single-Threaded Apartment Part 2 - CodeProject