Returning a value from Dispatcher.RunAsync() to background thread
.net, c#, windows-store-apps
Solution
You could make use of the `ManualResetEvent` class.
This is my helper method for returning values from the UI thread to other threads. This is for Silverlight! As such, you probably can't copy-paste it to your application and expect it to work, BUT hopefully it'll give you an idea on how to proceed.
public static T Invoke<T>(Func<T> action)
{
if (Dispatcher.CheckAccess())
return action();
else
{
T result = default(T);
ManualResetEvent reset = new ManualResetEvent(false);
Dispatcher.BeginInvoke(() =>
{
result = action();
reset.Set();
});
reset.WaitOne();
return result;
}
}
Problem
I'm using Dispatcher.RunAsync() to show a MessageDialog from a background thread. But I'm having trouble figuring out how to get a result returned. My code: ``` bool response = false; await dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, async () => { DebugWriteln("Showing confirmation dialog: '" + s + "'."); MessageDialog dialog = new MessageDialog(s); dialog.Commands.Add(new UICommand(GetLanguageString("Util_DialogButtonYes"), new UICommandInvokedHandler((command) => { DebugWriteln("User clicked 'Yes' in confirmation dialog"); response = true; }))); dialog.Commands.Add(new UICommand(GetLanguageString("Util_DialogButtonNo"), new UICommandInvokedHandler((command) => { DebugWriteln("User clicked 'No' in confirmatoin dialog"); response = false; }))); dialog.CancelCommandIndex = 1; await dialog.ShowAsync(); }); //response is always False DebugWriteln(response); ``` Is there anyway to do it like this? I thought about maybe returning the value from inside RunAsync() but function is void.