Chapter 19

Threading and Synchronization

There are several reasons for using threading. Suppose that you are making a network call from an application that might take some time. You don’t want to stall the user interface and just let the user wait until the response is returned from the server. The user could do some other actions in the meantime or even cancel the request that was sent to the server. Using threads can help.

For all activities that require a wait — for example, because of a file, database, or network access — a new thread can be started to fulfill other tasks at the same time. Even if you have only processing-intensive tasks to do, threading can help. Multiple threads of a single process can run on different CPUs, or, nowadays, on different cores of a multiple-core CPU, at the same time.

You must be aware of some issues when running multiple threads, however. Because they can run during the same time, you can easily get into problems if the threads access the same data. You must implement synchronization mechanisms.

This chapter provides the foundation you will need when programming applications with multiple threads, including:

  • An overview of threading
  • Lightweight threading using delegates
  • Thread class
  • Thread pools
  • Threading issues
  • Synchronization techniques
  • Timers
  • COM apartments
  • Event-based asynchronous pattern


A thread is an independent stream of instructions in a program. All your C# programs up to this point have one entry point — the Main() method. ...

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