Advantages of Serviced Components

Windows Component Services provide a hosting environment for middle-tier components. In a 3-tier application design, code is separated into a user interface tier, a business logic tier and a data access tier. The middle-tier components provide the business logic of your application This hosting environment provides the basic infrastructure to support middle-tier components and help to optimize them for performance and availability to a large number of users. Some of the features of Windows Component Services help you to manage distributed transactions, enforce role-based security, and increase performance by using object pooling. Other features such as message queuingand event notification provide additional options for application design. These features will be covered in more detail later in this chapter. As a developer, you can take advantage of these features very easily and concentrate on writing code to solve your specific business problems, without worrying about the complexities of transaction management or security authentication schemes. By taking advantage of these services, you enable your applications to achieve better performance, reliability, and scalability with a minimum of coding on your part.

The History of Component Services

The idea for a standard component infrastructure was first introduced with the Windows NT 4.0 Option Pack. Microsoft Transaction Server (MTS) and Microsoft Message Queue Server (MSMQ) were included in the Windows NT option pack. MTS, due to its name, was mostly seen as a means to support distributed transactions (transactions involving more than one component, perhaps even running on different servers), but it also provided security and performance features. MSMQ works in conjunction with MTS, providing for asynchronous message-based communication within transactions.

Windows 2000 improved on MTS and MSMQ by adding new features and integrating more tightly with the operating system. At this point, the name was also changed to Component Services to reflect that this infrastructure did far more than just manage transactions. COM technology also received an update and is now known as COM+. When we create .NET distributed applications that use Component Services, there is another name that we can use: .NET Enterprise Services.

Another important concept to understand about Component Services is that of the declarative model of requesting, rather than a procedural, code-based approach. The Component Services management console (which you will try out later in the chapter) provides many options to be set by an administrator. For example, if your application’s security requirements change after the application is in production, the server administrator can make these changes in the management console. The component does not have to be updated at the source-code level.

When developing components with the .NET Framework, you can also apply attributes in your source code at the assembly, class, or method level to control the component’s behavior when it is running under Component Services. All .NET components that will run under Windows Component Services must inherit from the System.EnterpriseServices.ServicedComponent base class.