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Professional Visual Basic® 2008 by Bill Sheldon, Kent Sharkey, Bill Evjen, Billy Hollis

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Chapter 25. Working with Classic COM and Interfaces

However much we try, we just cannot ignore the vast body of technology surrounding Microsoft's Component Object Model (COM). Over the years, this model has been the cornerstone of so much Microsoft-related development that we have to take a long, hard look at how we are going to integrate all that technology into the world of .NET.

This chapter begins by taking a brief backward glance at COM, and then compares it with the way that components interact in .NET. It also takes a look at the tools Microsoft provides to help link the two together. Having looked at the theory, you then try it out by building a few example applications. First you take a legacy basic COM object and run it from a Visual Basic 2008 program. Then you repeat the trick with a full-blown ActiveX control. Finally, you run some Visual Basic code in the guise of a COM object.

More information on how to make COM and VB6 code interoperate with the .NET platform can be found in Professional Visual Basic Interoperability: COM and VB6 to .NET (Wiley, 2002).

As you do all that, keep in mind one thing: COM is, to a large extent, where .NET came from. In addition, with all the time and resources that have been invested in this technology, it is important to consider the best ways to both maintain these investments and integrate them into new investments you make.

Understanding COM

Before looking into the COM-.NET interoperability story, it is important to understand COM's main ...

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