Channel 9 Forums - Tech Off - Nested Task.Factory.StartNew() creates the task on the UI thread http://mschnlnine.vo.llnwd.net/d1/Dev/App_Themes/C9/images/feedimage.png Channel 9 Forums - Tech Off - Nested Task.Factory.StartNew() creates the task on the UI thread http://channel9.msdn.com/Forums Channel 9 keeps you up to date with the latest news and behind the scenes info from Microsoft that developers love to keep up with. From LINQ to SilverLight – Watch videos and hear about all the cool technologies coming and the people behind them. http://channel9.msdn.com/Forums en Wed, 22 May 2013 06:55:40 GMT Wed, 22 May 2013 06:55:40 GMT Rev9 6 -6 -1 Tech Off - Nested Task.Factory.StartNew() creates the task on the UI thread I have some code that uses Task.Factory.StartNew() to start a background task when the user clicks a button. Upon completion, the background task then calls Task.Factory.StartNew() but specifies the UI thread context in order to update the UI with the results.

This work fine. However now I have a UI option that will allow the task to run repeatedly until the user cancels it. So now in the second Task.Factory.StartNew() that runs the task on the UI thread, I just call the first function that starts the background task again. However what I'm finding is that the second time around, the first Task.Factory.StartNew() runs the task on the UI thread even though I did not pass in a thread context to it. I'm not sure it matters, but I'm passing in TaskCreationOptions.LongRunning as well for both calls.

To put it another way... In both cases the first Task.Factory.StartNew() was called from the UI thread. The 1st time, it runs the task on a background thread. The second time, on the UI thread. Exact same code and parameters.

Any ideas why this would be happening?

]]> http://channel9.msdn.com/Forums/TechOff/Nested-TaskFactoryStartNew-creates-the-task-on-the-UI-thread/84e69ea2ed2e4d96bfcfa0ed013b8229#84e69ea2ed2e4d96bfcfa0ed013b8229 Wed, 17 Oct 2012 19:08:43 GMT http://channel9.msdn.com/Forums/TechOff/Nested-TaskFactoryStartNew-creates-the-task-on-the-UI-thread/84e69ea2ed2e4d96bfcfa0ed013b8229#84e69ea2ed2e4d96bfcfa0ed013b8229 BitFlipper 6 http://channel9.msdn.com/Niners/BitFlipper/Discussions/RSS Tech Off - Nested Task.Factory.StartNew() creates the task on the UI thread Looks like I'm running into this problem. However I'm not using the ContinueWith call, so I'm not sure how to fix my issue. I'm essentially making a nested call to Task.Factory.StartNew().

]]> http://channel9.msdn.com/Forums/TechOff/Nested-TaskFactoryStartNew-creates-the-task-on-the-UI-thread/a043105b01254bb59c1fa0ed013eca29#a043105b01254bb59c1fa0ed013eca29 Wed, 17 Oct 2012 19:20:40 GMT http://channel9.msdn.com/Forums/TechOff/Nested-TaskFactoryStartNew-creates-the-task-on-the-UI-thread/a043105b01254bb59c1fa0ed013eca29#a043105b01254bb59c1fa0ed013eca29 BitFlipper 6 http://channel9.msdn.com/Niners/BitFlipper/Discussions/RSS Tech Off - Nested Task.Factory.StartNew() creates the task on the UI thread OK I solved the problem by passing in TaskScheduler.Default into the 2nd [fixed it] Task.Factory.StartNew() call.

]]> http://channel9.msdn.com/Forums/TechOff/Nested-TaskFactoryStartNew-creates-the-task-on-the-UI-thread/aa5570dd4c7a456a9202a0ed0142e1b4#aa5570dd4c7a456a9202a0ed0142e1b4 Wed, 17 Oct 2012 19:35:34 GMT http://channel9.msdn.com/Forums/TechOff/Nested-TaskFactoryStartNew-creates-the-task-on-the-UI-thread/aa5570dd4c7a456a9202a0ed0142e1b4#aa5570dd4c7a456a9202a0ed0142e1b4 BitFlipper 6 http://channel9.msdn.com/Niners/BitFlipper/Discussions/RSS Tech Off - Nested Task.Factory.StartNew() creates the task on the UI thread [TaskScheduler.Default] puts the first thread at a known location so that it can be found for the next thread evoked? How does it work?

]]> http://channel9.msdn.com/Forums/TechOff/Nested-TaskFactoryStartNew-creates-the-task-on-the-UI-thread/90c4d8f0adb544759b4ca0ed01440a6d#90c4d8f0adb544759b4ca0ed01440a6d Wed, 17 Oct 2012 19:39:47 GMT http://channel9.msdn.com/Forums/TechOff/Nested-TaskFactoryStartNew-creates-the-task-on-the-UI-thread/90c4d8f0adb544759b4ca0ed01440a6d#90c4d8f0adb544759b4ca0ed01440a6d JohnAskew 6 http://channel9.msdn.com/Niners/JohnAskew/Discussions/RSS Tech Off - Nested Task.Factory.StartNew() creates the task on the UI thread

, JohnAskew wrote

[TaskScheduler.Default] puts the first thread at a known location so that it can be found for the next thread evoked? How does it work?

I have no idea. But it fixed my issue.

]]> http://channel9.msdn.com/Forums/TechOff/Nested-TaskFactoryStartNew-creates-the-task-on-the-UI-thread/a779b540bc9046d0ababa0ed0153f60d#a779b540bc9046d0ababa0ed0153f60d Wed, 17 Oct 2012 20:37:45 GMT http://channel9.msdn.com/Forums/TechOff/Nested-TaskFactoryStartNew-creates-the-task-on-the-UI-thread/a779b540bc9046d0ababa0ed0153f60d#a779b540bc9046d0ababa0ed0153f60d BitFlipper 6 http://channel9.msdn.com/Niners/BitFlipper/Discussions/RSS Tech Off - Nested Task.Factory.StartNew() creates the task on the UI thread

, BitFlipper wrote

*snip*

I have no idea. But it fixed my issue.

Ah you are correct. Sorry that was a typo. I'm passing TaskScheduler.Default into the 2nd call.

]]> http://channel9.msdn.com/Forums/TechOff/Nested-TaskFactoryStartNew-creates-the-task-on-the-UI-thread/95d8a523adfc4f738d5ba0ed01584b0c#95d8a523adfc4f738d5ba0ed01584b0c Wed, 17 Oct 2012 20:53:31 GMT http://channel9.msdn.com/Forums/TechOff/Nested-TaskFactoryStartNew-creates-the-task-on-the-UI-thread/95d8a523adfc4f738d5ba0ed01584b0c#95d8a523adfc4f738d5ba0ed01584b0c BitFlipper 6 http://channel9.msdn.com/Niners/BitFlipper/Discussions/RSS