Microsoft .NET Framework 3.5 Windows Communication Foundation: Sessions and Instancing

9/24/2008

Contents

This chapter from MCTS Self-Paced Training Kit (Exam 70-503): Microsoft .NET Framework 3.5 Windows Communication Foundation answers the question of how sessions function within the WCF world. It also describes the various instancing options and the implications each choice has on the available functionality.

When a discussion of Windows Communication Foundation (WCF) turns to the concepts and details of sessions and instancing, it seems as though you’re starting to tread on common ground with Web developers. ASP.NET developers are likely to be familiar with the concepts associated with sessions. Although less directly, ASP.NET developers also deal with some of the aspects associated with instancing in relation to having a Web site hosted on a Web farm. However, the instancing issues will be more familiar to developers who have used .NET remoting in the past.

This chapter finds common ground for all developers, regardless of their background, and answers the question of how sessions function within the WCF world. It also describes the various instancing options and the implications each choice has on the available functionality. This content is definitely part of the certification exam; however, pay close attention because it is also frequently at the heart of real-world design choices.

Exam objectives in this chapter:

Manage instances.
Manage sessions.

Lessons in this chapter:

Lesson 1: Instancing Modes
Lesson 2: Working with Instances

Before You Begin

To complete the lessons in this chapter, you must have:

A computer that meets or exceeds the minimum hardware requirements listed in the introduction at the beginning of the book.
Any edition of Microsoft Visual Studio 2008 (including Microsoft Visual C# 2008 Express edition or Microsoft Visual Basic 2008 Express edition) installed on the computer.

Real World

Bruce Johnson

The session side of this chapter is, again, probably familiar to those of you who have worked with ASP.NET. The idea is a simple one: By allowing the service to identify the client that made a request, it becomes possible to save state information with that client. This information can facilitate sophisticated interactions between the client and the service. What is nice about the session model that WCF provides is that the binding is, for the most part, irrelevant. Like so much else in WCF, the details are hidden from view, and it just works.

The instancing side of this chapter is a little different. It’s more in the category of “what you need to know to be an expert.” In most cases, you will not need to know the details of instancing beyond the need to set the mode to per call, per session, or singleton, but within that world, some strange things have been known to happen. You are moving into an area in which subtle bugs can arise, and if you have the detailed knowledge provided in this chapter, you will be able to identify the source of the problem more quickly and give off the heroic aura that experts are expected to have.

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