In Brief

This chapter examined the key programming tasks that as a .NET developer you will face regarding interoperating with existing technologies, particularly Microsoft COM/COM+ components . Here's an overview of this chapter's topics:

• Interoperability with Microsoft's existing and legacy technologies, including COM/COM+ components and ActiveX controls, has been given a significant amount of importance in the design and implementation of the .NET platform.

• The .NET Framework provides bidirectional integration of COM;.NET COM objects can be used within .NET components, and .NET assemblies can be exposed as COM type libraries.

• In most scenarios, tools automate the process of creating the required interoperability wrapper code. However, techniques are in place if a developer wants finer control of the marshaling and wrapping processes.

• Visual Studio .NET provides an integrated set of tools for invoking existing COM objects from .NET applications or even leveraging newly developed .NET components in applications developed using COM/COM+ technologies. However, if you are not using Visual Studio .NET, the same set of tools is available from the .NET Frame- work SDK.

• Platform Invocation Services (better known as PInvoke) allow .NET programming languages to access Win32 DLLs by providing appropriate method signatures. However, the process of using platform DLLs is significantly more involved than COM interoperability.

• Web services and XML technologies provide an alternative way of clearly separating the two technologies to run in their own environments, yet connect by a technology- independent set of Web services standards, including SOAP and WSDL. COM objects can be used with the .NET Framework by using the Microsoft SOAP Toolkit.