Visual Basic 2005: A Developer's Notebook

Handle Asynchronous Tasks Safely

One of .NET's most impressive features is its extensive support for multithreaded programming. However, as most programmers discover at some point in their lives, multithreaded programming isn't necessarily easy.

Note

Need to conduct a time-consuming task in the background without dealing with threading issues? The new BackgroundWorker class makes it easy.

One of the main challenges with Windows applications is that it's not safe to modify a form or control from a background thread, which means that after your background task is finished, there's no straightforward way to update your application's interface. You can use the Control.Invoke( ) method to marshal a method to the correct thread, but other problems then appear, such as transferring the information you need to make the update. Fortunately, all of these headaches can be avoided thanks to the new BackgroundWorker component.

How do I do that?

The BackgroundWorker component gives you a foolproof way to run a time-consuming task on a separate, dedicated thread. This ensures that your application interface remains responsive, and it allows your code to carry out other tasks in the foreground. Best of all, the underlying complexities of multithreaded programming are hidden. Once the background process is complete, you simply handle an event, which fires on the main thread. In addition, the BackgroundWorker supports progress reporting and canceling.

You can either create a BackgroundWorker object ...