In Chapter 4, you learned techniques for making your .NET components accessible to unmanaged applications through COM. You can use many of these same techniques, with a little augmentation , to make your .NET components work in the COM+ environment as well. The purpose of this chapter is to provide you with the knowledge required to understand the relationship between COM, DCOM, COM+, and .NET. Understanding these relationships is important if you want to create a functional COM+ application.
Remember that COM+ relies on COM and DCOM (Microsoft Distributed Component Object Model) to provide part of its functionality. COM is the source of component technology, while DCOM provides the remote procedure call (RPC) functionality. The first two sections of this chapter explore the relationship between the two. The chapter will also discuss how Microsoft Message Queuing (MSMQ) fits within the COM+ Queued Components . Using message queuing can greatly enhance the flexibility of your application and allow it to process data asynchronously.
The final portion of the chapter discusses some COM+-specific issues you need to consider when working with .NET components. For example, the communication with COM+ is two way, so you need to know how to accept as well as send information to COM+. In general, youll find that the hardest thing to understand is the communication specifically , how it occursbecause .NET performs part of the work for you in the background.