Properly check for thread access on UWP (#332)

* Properly check for thread access on UWP * Do some null checks with UWP * #292 seems to have been lost
xamarin · Jun 26, 2018 · 7e3e6a7 · 7e3e6a7
1 parent 37bb821
commit 7e3e6a7
Showing 1 changed file with 6 additions and 3 deletions.
diff --git a/Xamarin.Essentials/MainThread/MainThread.uwp.cs b/Xamarin.Essentials/MainThread/MainThread.uwp.cs
@@ -7,13 +7,16 @@ namespace Xamarin.Essentials
     public static partial class MainThread
     {
         static bool PlatformIsMainThread =>
-            CoreApplication.MainView.CoreWindow.Dispatcher == null;
+            CoreApplication.MainView.CoreWindow?.Dispatcher?.HasThreadAccess ?? false;
 
         static void PlatformBeginInvokeOnMainThread(Action action)
         {
-            var dispatcher = CoreApplication.MainView.CoreWindow.Dispatcher;
+            var dispatcher = CoreApplication.MainView.CoreWindow?.Dispatcher;
 
-            if (dispatcher != null)
+            if (dispatcher == null)
+                throw new InvalidOperationException("Unable to find main thread.");
+
+            if (!dispatcher.HasThreadAccess)
                 dispatcher.RunAsync(CoreDispatcherPriority.Normal, () => action()).WatchForError();
             else
                 action();