Long time ago I wrote about HOWTO: Know the actual type behind a System.__ComObject type returned by an .Object property since chances are that you are going to find System._ComObject when using Visual Studio automation (because internally it’s all COM).

Last January 2009 Lucian Wischik, the Visual Basic Specification Lead, wrote an article in MSDN Magazine about Inspecting COM Objects With Reflection, which can be useful if you are unable to get the assembly DLL that contains the actual type behind System._ComObject to perform the cast and you need to use Reflection against the _COMObject to get its properties, call its methods, etc.