Comments on: Synchronizing .NET 4 Tasks with the UI Thread http://reedcopsey.com/2009/11/17/synchronizing-net-4-tasks-with-the-ui-thread/ Thoughts on C#, WPF, .NET, and programming for Scientific Visualization Sat, 04 Sep 2010 01:57:48 +0000 hourly 1 http://wordpress.org/?v=3.0.1 By: <img src='http://reedcopsey.com/blog/wp-content/plugins/rpx/images/openid.png'/> Reed http://reedcopsey.com/2009/11/17/synchronizing-net-4-tasks-with-the-ui-thread/#comment-1121 Reed Tue, 06 Jul 2010 17:58:18 +0000 http://reedcopsey.com/?p=88#comment-1121 Tillias, That's actually not accurate. The default TaskScheduler, which is what is used when you do Task.Factory.StartNew, will use always use a ThreadPool thread to execute your Task, unless the LongRunning hint is specified, in which case it will use a dedicated thread (in .NET 4's implementation). Either way, it should NEVER run on the UI thread, since the UI thread should never be on a ThreadPool thread. Tasks will only get scheduled on the current thread when the current thread is a threadpool thread, or the current thread is blocking on the result of a collection of Tasks (including the one that needs to execute). That being said, if you want to force a task to run on a dedicated thread, you can do so by specifying the LongRunning hint (in the current implementation). This is a much simpler alternative to creating a custom TaskScheduler. Using an STA thread scheduler is really overkill, unless you specifically need an STA thread. -Reed Tillias,

That’s actually not accurate. The default TaskScheduler, which is what is used when you do Task.Factory.StartNew, will use always use a ThreadPool thread to execute your Task, unless the LongRunning hint is specified, in which case it will use a dedicated thread (in .NET 4′s implementation). Either way, it should NEVER run on the UI thread, since the UI thread should never be on a ThreadPool thread.

Tasks will only get scheduled on the current thread when the current thread is a threadpool thread, or the current thread is blocking on the result of a collection of Tasks (including the one that needs to execute).

That being said, if you want to force a task to run on a dedicated thread, you can do so by specifying the LongRunning hint (in the current implementation). This is a much simpler alternative to creating a custom TaskScheduler. Using an STA thread scheduler is really overkill, unless you specifically need an STA thread.

-Reed

]]> By: tillias http://reedcopsey.com/2009/11/17/synchronizing-net-4-tasks-with-the-ui-thread/#comment-1120 tillias Tue, 06 Jul 2010 17:10:53 +0000 http://reedcopsey.com/?p=88#comment-1120 Hi Reed! Task doesn't guarantee that it will be executed in separate thread. I've faced several common scenarios where Task's delegate is executed in GUI thread and thus the application is stuck. Custom TaskScheduler must be used in order to guarantee that task will be executed in separate thread ( and not in the same GUI one). You can reed about it here: http://tillias.wordpress.com/2010/07/05/net-4-system-threading-tasks-and-wpf-ui-thread/ Hi Reed!
Task doesn’t guarantee that it will be executed in separate thread. I’ve faced several common scenarios where Task’s delegate is executed in GUI thread and thus the application is stuck. Custom TaskScheduler must be used in order to guarantee that task will be executed in separate thread ( and not in the same GUI one).

You can reed about it here: http://tillias.wordpress.com/2010/07/05/net-4-system-threading-tasks-and-wpf-ui-thread/

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