Wednesday, February 15, 2012

Using Parallelism in .NET WinForm applications

We all have gone through the travials of multi-threaded programming in WinForm applications. The challenge in WinForm applications is that the UI controls are bound to the thread that created/rendered them; i.e. the UI control can only by updated by the main thread or the GUI thread that created it.

But to keep the UI responsive, we cannot execute any long running task (>0.5 sec) on the UI thread, else the GUI would hang or freeze. If we run the business logic asynchronously on another thread, then how do we pass the results back to the main GUI thread to update the UI?

Traditionally this has been done using the Control.Invoke() methods. More details on this approach is available on this link: http://msdn.microsoft.com/en-gb/magazine/cc300429.aspx

But with the introduction of TPL, there is another alternative way of doing this. We can use the TaskScheduler and SynchronizationContext classes to call heavy lifting work and then pass the results to the main GUI thread.

For e.g.
TaskScheduler uiScheduler = 
           TaskScheduler.FromCurrentSynchronizationContext();
new Task({Your code here}).start(uiScheduler);

Given below are 2 excellent articles eloborating this in detail:
http://www.codeproject.com/Articles/152765/Task-Parallel-Library-1-of-n

http://reedcopsey.com/2010/03/18/parallelism-in-net-part-15-making-tasks-run-the-taskscheduler/

Sacha Barber has an excellent 6 series article on the intricacies of TPL, which I loved reading.