Integrating with COM+
This chapter is about working with the past. That past is based upon component technology created by Microsoft to provide, at first, a desktop-oriented protocol for reusing application logic. That technology expanded into a distributed technology that helped better position Microsoft in the enterprise and provide a challenge to competing technologies.
Not without faults, numerous applications were developed based upon this component technology. As a result, we can't forget the amount of investment by enterprises in this technology. It would damage Microsoft's credibility and the marketability if Microsoft introduced a new technology that would force an enterprise to scrap its original investments. Therefore, Microsoft and the WCF team worked hard to provide an evolutionary, as opposed to revolutionary, approach for bridging the technological divide, never forgetting the famous quote "Those who cannot remember the past are condemned to repeat it." []
[] Attributed to George Santayana, 19th-century philosopher
Introduced in 1993, Component Object Model (COM) was the basis for other emerging technologies from Microsoft such as Object Linking and Embedding (OLE), ActiveX, and Distributed COM (DCOM). COM was initially introduced to compete with Common Object Request Broker Architecture (CORBA), a language-independent and cross-platform distributed system technology. They did share some core principles, but they were not compatible. Concepts and techniques such as Interface Definition Language (IDL) are present in both technologies. But, binary interoperability didn't exist.
COM+, introduced in 1998, was more of ancillary technology that worked with COM but did not replace it. Key features of COM+ are transactional components, queued components, role-based security, and object pooling. COM+ 1.5 added features such as application pooling, SOAP services, services without components, and some other features.[]
[] You can learn more in the topic "What's new in COM+ 1.5" on MSDN at http://msdn.microsoft.com/library/en-us/cossdk/html/e7073ba5-6b19-4d94-8cc0-b4e16bb44afd.asp.
Today, COM+ 1.5 is a core part of the Windows platform. Even with the .NET base class library (BCL) COM interoperability still occurs. Runtime callable wrappers (RCW) are used throughout the .NET BCL-one prime example in .NET 2.0 is the web browser control, which is, as stated in the MSDN documentation, a managed wrapper for the web browser's ActiveX control. Additionally, serviced components use COM+ transactions.