Why does this Parallel.ForEach code freeze the program up?

Question

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This code grabs a number of proxies from the list in the main window (I couldn\'t figure out how to make variables be available between diffe

Answer 1

This is what I think might be happening in your code-base.

Normal Scenario : You click on button. Do not use Parallel.Foreach loop. Use Dispatcher class and push the code to run on separate thread in background. Once the background thread is done processing, it will invoke the main UI thread for updating the UI. In this scenario, the background thread(invoked via Dispatcher) knows about the main UI thread, which it needs to callback. Or simply said the main UI thread has its own identity.

Using Parallel.Foreach loop : Once you invoke Paralle.Foreach loop, the framework uses the threadpool thread. ThreadPool threads are chosen randomly and the executing code should never make any assumption on the identity of the chosen thread. In the original code its very much possible that dispatcher thread invoked via Parallel.Foreach loop is not able to figure out the thread which it is associated with. When you use explicit thread, then it works fine because the explicit thread has its own identity which can be relied upon by the executing code.

Ideally if your main concern is all about keeping UI responsive, then you should first use the Dispatcher class to push the code in background thread and then in there use what ever logic you want to speedup the overall execution.