CODEWITHSUNDEEP
c#.netwpfmultithreadingtask-parallel-library
Muhammad Adnan
Muhammad Adnan

Reputation: 1375

c# accessing ui elements in Task without using dispatcher

I'm hoping to find a mechanism for accessing/manipulating a ui element (like textbox) properties in a separate Thread but accessing it using Dispatcher means giving control to UI thread which keeps the user from doing anything (which is something I don't want - to freeze ui..)

So I actually want to access the ui from a separate thread without needing to freeze the main UI thread.

Upvotes: 0

Views: 966

Answers (2)

bradgonesurfing
bradgonesurfing

Reputation: 32202

You cannot access the dependency properties of UI elements on another thread. It is not allowed.

However updating a text property is blindingly fast and that is most likely not your bottleneck. Calculating what the value of that text property is may be slow. So for example if you have an event triggered from the UI you can spawn a task which will run on another thread and keep the UI responsive.

When the value is ready the code on the left hand side of the await will run on the UI thread and you can then modify any UI properties you wish.

SomeEvent += async (s,e) => {

   var text = await Task.Run(()=>{
    return SomeVeryExpensiveOperation();          
   });

   MyTextBox.Text = text;

}

A more worked out example is here

http://www.codearsenal.net/2012/11/csharp-5-async-and-await-example.html#.WLhBlm_ysUE

Upvotes: 5

AnjumSKhan
AnjumSKhan

Reputation: 9827

In your case, you have to use static class with static events, fire events from your Task and handle the event in your ViewModel / Codebehind, and do whatever you want in that event handler.

Upvotes: -3

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