O'Reilly Book Excerpts: COM and .NET Component Services
.NET Serviced Componentsby Juval Löwy
This excerpt is Chapter 10 from COM and .NET Component Services, published in September 2001 by O'Reilly.
.NET is the new platform from Microsoft used to build component-based applications, from standalone desktop applications to web-based applications and services. The platform will be available on forthcoming Microsoft operating systems and supported by the next release of Visual Studio, called Visual Studio.NET. In addition to providing a modern object-oriented framework for building distributed applications, .NET also provides several specialized application frameworks. These frameworks include Windows Forms for rich Windows clients, ADO.NET for data access, and ASP.NET for dynamic web applications. Another important framework is Web Services, which is used to expose and consume remote objects using the emerging SOAP and other XML-based protocols.
.NET is Microsoft's next-generation component technology. It is designed from the ground up to simplify component development and deployment, as well as to support interoperability between programming languages.
Despite its innovations and modern design, .NET is essentially a component technology. Like COM, .NET provides you with the means to rapidly build binary components, and Microsoft intends for .NET to eventually succeed COM. Like COM, .NET does not provide its own component services. Instead, .NET relies on COM+ to provide it with instance management, transactions, activity-based synchronization, granular role-based security, disconnected asynchronous queued components, and loosely coupled events. The .NET namespace that contains the types necessary to use COM+ services was named System.EnterpriseServices to reflect the pivotal role it plays in building .NET enterprise applications.
A .NET component that uses COM+ services is called a serviced component to distinguish it from the standard managed components in .NET. If you are not familiar with .NET, you should first read Appendix C or pick up a copy of .NET Framework Essentials by Thuan Thai and Hoang Lam (O'Reilly, 2001).
If you are already familiar with the basic .NET concepts, such as the runtime, assemblies, garbage collection, and C# (pronounced "C sharp"), continue reading. This chapter shows you how to create .NET serviced components that can take advantage of the COM+ component services that you have learned to apply throughout this book.
Table of Contents
- Developing Serviced Components
- .NET Assemblies and COM+ Applications
- Registering Assemblies
- Configuring Serviced Components
- Application Activation Type
- The Description Attribute
- Accessing the COM+ Context
- COM+ Context Attributes
- COM+ Object Pooling
- COM+ Just-in-Time Activation
- COM+ Constructor String
- COM+ Transactions
- COM+ Synchronization
- Programming the COM+ Catalog
- COM+ Security
- COM+ Queued Components
- COM+ Loosely Coupled Events