add issue for thread exception.

samples/ControlCatalog/MainWindow.xaml.cs

@@ -1,18 +1,26 @@
 using Avalonia;
 using Avalonia.Controls;
 using Avalonia.Markup.Xaml;
+using Avalonia.Threading;
+using ReactiveUI;
 using System;
+using System.Reactive.Linq;
+using System.Threading;
 
 namespace ControlCatalog
 {
     public class MainWindow : Window
     {
+		private Thread _initialThread;
+
         public MainWindow()
         {
             this.InitializeComponent();
             this.AttachDevTools();
-            //Renderer.DrawFps = true;
-            //Renderer.DrawDirtyRects = Renderer.DrawFps = true;
+            Renderer.DrawFps = true;
+            Renderer.DrawDirtyRects = Renderer.DrawFps = true;
+
+			_initialThread = Thread.CurrentThread;
         }
 
         private void InitializeComponent()
@@ -23,6 +31,22 @@ namespace ControlCatalog
             var theme = new Avalonia.Themes.Default.DefaultTheme();
             theme.TryGetResource("Button", out _);
             AvaloniaXamlLoader.Load(this);
+
+            var timer = new DispatcherTimer
+            {
+                Interval = TimeSpan.FromSeconds(1),
+            };
+
+            Observable.FromEventPattern(timer, nameof(timer.Tick)).Throttle(TimeSpan.FromMilliseconds(500)).ObserveOn(RxApp.MainThreadScheduler).Subscribe(_ =>
+            {
+                if (Thread.CurrentThread != _initialThread)
+                {
+                    throw new SystemException();
+                }
+            });
+
+            timer.Start();
+
         }
     }
 }