"COM and .NET Interoperability" covers working with COM components in .NET and .NET components in COM from basic topics like Runtime Callable Wrappers to advanced topics such as manual marshaling of data types between .NET and COM. This book is available in its entirety as a download to registered TSS.NET readers.

The book starts off with an introduction/review of COM concepts such as IUnknown, IClassFactory, and IDispatch interfaces as well as Active Template Library and IDL.

COM servers also support a special sort of COM type termed a class factory (also termed a class object). COM class factories also support the mandatory IUnknown, as well as another standard interface named IClassFactory. This interface allows the COM client to create a given coclass in a language- and locationneutral manner. As you may be aware, it is possible for a COM class factory to support the IClassFactory2 interface (which derives from ClassFactory).

The book moves on to cover the basics of .NET to COM interoperability before building on that with more advanced topics such as handling Variants and manually destroying a COM object.

The COM VARIANT data type is one of the most useful (and most hated) constructs of classic COM. The VARIANT structure is useful in that it is able to assume the identity of any [oleautomation]-compliant IDL type, which may be reassigned after the initial declaration. VARIANTs are hated for much the same reason, given that these dynamic transformations take time. Nevertheless, you are bound to run into a coclass that makes use of this type, and you would do well to understand how it maps into terms of .NET.

Authors

Andrew Troelsen is a partner, trainer, and consultant at Intertech-Inc., and is a leading authority on both .NET and COM. His book C# and the .NET Platform won the prestigious 2003 Referenceware Excellence Award and is now in its second edition. Also of note are his earlier five-star treatment of traditional COM in the bestselling Developer's Workshop to COM and ATL mirrored in his book, COM and .NET Interoperability, and his top-notch investigation of VB .NET in Visual Basic .NET and the .NET Platform: An Advanced Guide. Troelsen has a degree in mathematical linguistics and South Asian studies from the University of Minnesota and is a frequent speaker at numerous .NET-related conferences. He currently lives in Minneapolis, Minnesota, with his wife, Amanda, and spends his free time investigating .NET and waiting for the Wild to win the Stanley Cup.