Unhandled Exception: System.InvalidOperationException: The Dispatcher is unable to request processing. This is often because the application has starved the Dispatcher's message pump. Is thrown from Windows base dll.

Question

Unhandled Exception: System.InvalidOperationException: The Dispatcher is unable to request processing. This is often because the application has starved the Dispatcher's message pump. Is thrown from Windows base dll.

Raja Vignesh 1

Hi ,

We have a project attached with the sample. We use dispatchers in the project to made the changes to the sample’s UI. We also start a dispatcher timer with 5 milliseconds which ran until the application runs. In the Tick event of the dispatcher timer we handle the virtualization process. If we ran the sample along with the application normally, it runs properly without any error.

But if we set the HandleDispatcherRequestProcessingFailure property in the sample side, the “Unhandled Exception: System.InvalidOperationException: The Dispatcher is unable to request processing. This is often because the application has starved the Dispatcher's message pump” exception throws and the application breaks. We tried to handle the error in the DispatcherUnhandled event in the App.xaml.cs class file and also in the thread in which the dispatcher is invoked but it is not get caught by the event in any of the places. We have also tried the try/catch block for the dispatchers used in the project, but nothing works. We have also checked whether the error is got in the runWorker_completed event, but it also not worked. How to catch the exception in DispatcherUnhandled event or handle the exception in the sample side?

Thanks.

Hui Liu-MSFT 48,711 Reputation points Microsoft External Staff

2022-07-28T07:15:33.863+00:00

Hi,@Raja Vignesh . Welcome Microsoft Q&A.
Could you provide me with a minimal example that reproduces the problem to analyze? Can you show the code and steps you have tried? You can also try and see if thread 1 and thread 2 are helpful to you.
Raja Vignesh 1 Reputation point

2022-07-30T13:52:06.28+00:00

Hi @Hui Liu-MSFT ,

Thanks for your suggestion. But we couldn’t able to catch the exception in the Dispatcher.UnhandledException event. The exception is cought in the AppDomain.UnhandledException event but we can’t handle this in it. I have attached the sample structure below.In the Sample Side(Dispatcher_Sample), we are setting the property

BaseCompatibilityPreference.HandleDispatcherProcessingFailure property.(The fact is that if we set the property in sample, the exception is thrown but if we remove it the exception is not thrown). In the project file, we have a DispatcherTimer obect and its Tick event will be triggered for every 5 milliseconds. We call the dispatcher in the project file in many places as below. UI object.Dispatcher.Invoke((Action)(()=>{//Performs the UI related action})) ;I have also tried the BeginInvoke methode instead of invoke but nothing works. I have tried the try/catch blocks in the action part of the dispatcher, it also not works. We also have a separate UIDispatcher class which calls the Begin Invoke method.

Thanks in advance.