41.7. Threads

Most applications make use of multiple threads at some point. In particular for Windows applications, in order for the user interface to always appear responsive, it is important to run time-consuming tasks on a thread separate from the main application. Of course, concurrent execution of threads makes debugging more difficult, especially when the threads are accessing the same classes and methods.

Figure 41-9 shows the Threads window, which lists all the active threads for a particular application. Notice that in addition to the threads created in the code, additional background threads have been created by the debugger. For simplicity, the threads used by this application, including the main user interface thread, have been given names so they can easily be distinguished.

Figure 41.9. Figure 41-9

The Threads window shows a yellow arrow next to the thread that is currently being viewed in the code window. To navigate to another thread, simply double-click that thread to bring the current location of that thread into view in the code window and update the call stack to reflect the new thread.

In Break mode, all threads of an application are paused. However, when you are stepping through your code with the debugger, the next statement to be executed may or may not be on the same thread you are interested in. If you are only interested in the execution path of a single thread, and the execution of other threads can be suspended, right-click the thread in the Threads window and select Freeze from the context menu. To resume the suspended thread, select Thaw from the same menu.

Debugging multi-threaded applications is explained further in Chapter 45.