CoInitializeEx initializes the COM library for use by the calling thread, sets the thread's concurrency model, and creates a new apartment for the thread if one is required. Values for the dwCoInit parameter are taken from the COINIT enumeration. However, since pinvoke is a dotNET construct you should be aware that dotNET already does a COM initialization and therefore calling a CoInitializeEx function most likely will not do what you expect. This problem occurs when trying to instantiate a COM object from within dotNET where the COM objects threading model is different from dotNETs. Search on Common Language Runtime or CLR and COINIT_APARTMENTTHREADED to find posts on this issue.

An IntPtr is a pointer to a memory location (unmanaged) that adapts to the platform it is running on (64-bit, etc.) UNLIKE a standard int/Integer. You should always use this type for unmanaged calls that require it, even though an int will appear to work on your development machine.