Professional Visual Basic® 2008

Chapter 26. Threading

One of the results of the move from 16-bit to 32-bit computing was the ability to write code that made use of threads, but although Visual C++ developers have been able to use threads for some time, Visual Basic developers have not had a truly reliable way to do so, until now. Previous techniques involved accessing the threading functionality available to Visual C++ developers. Although this worked, actually developing multithreaded code without adequate debugger support in the Visual Basic environment was nothing short of a nightmare.

For most developers, the primary motivation for multithreading is the ability to perform long-running tasks in the background while still providing the user with an interactive interface. Another common scenario is when building server-side code that can perform multiple long-running tasks at the same time. In that case, each task can be run on a separate thread, enabling all the tasks to run in parallel.

This chapter introduces you to the various objects in the .NET Framework that enable any .NET language to be used to develop multithreaded applications.

What Is a Thread?

The term thread really refers to thread of execution. When your program is running, the CPU is actually running a sequence of processor instructions, one after another. You can think of these sequential instructions as forming a thread that is being executed by the CPU. A thread is, in effect, a pointer to the currently executing instruction in the sequence of ...