Xaml Islands Fixes.

GazeInputTest/App.xaml.cs

@@ -2,8 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using Microsoft.Toolkit.Uwp.Input.GazeInteraction;
 using System;
+using Microsoft.Toolkit.Uwp.Input.GazeInteraction;
 using Windows.ApplicationModel;
 using Windows.ApplicationModel.Activation;
 using Windows.UI.Xaml;

GazeInputTest/MainPage.xaml.cs

@@ -2,8 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using Microsoft.Toolkit.Uwp.Input.GazeInteraction;
 using System;
+using Microsoft.Toolkit.Uwp.Input.GazeInteraction;
 using Windows.ApplicationModel.Core;
 using Windows.UI.Core;
 using Windows.UI.ViewManagement;

Microsoft.Toolkit.Uwp.Connectivity/BluetoothLEHelper/BluetoothLEHelper.cs

@@ -8,12 +8,12 @@
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
-using Windows.ApplicationModel.Core;
+using Microsoft.Toolkit.Uwp.Helpers;
 using Windows.Devices.Bluetooth;
 using Windows.Devices.Bluetooth.Advertisement;
 using Windows.Devices.Enumeration;
 using Windows.Foundation.Metadata;
-using Windows.UI.Core;
+using Windows.System;
 
 namespace Microsoft.Toolkit.Uwp.Connectivity
 {
@@ -59,11 +59,15 @@ public class BluetoothLEHelper
         /// </summary>
         private BluetoothAdapter _adapter;
 
+        private DispatcherQueue _dispatcherQueue;
+
         /// <summary>
         /// Prevents a default instance of the <see cref="BluetoothLEHelper" /> class from being created.
         /// </summary>
         private BluetoothLEHelper()
         {
+            _dispatcherQueue = DispatcherQueue.GetForCurrentThread();
+
 #pragma warning disable CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
             Init();
 #pragma warning restore CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
@@ -201,8 +205,7 @@ private async Task Init()
         /// <param name="args">The advertisement.</param>
         private async void AdvertisementWatcher_Received(BluetoothLEAdvertisementWatcher sender, BluetoothLEAdvertisementReceivedEventArgs args)
         {
-            await CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(
-                CoreDispatcherPriority.Normal,
+            await _dispatcherQueue.ExecuteOnUIThreadAsync(
                 () =>
                 {
                     if (_readerWriterLockSlim.TryEnterReadLock(TimeSpan.FromSeconds(1)))
@@ -217,7 +220,7 @@ await CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(
 
                         _readerWriterLockSlim.ExitReadLock();
                     }
-                });
+                }, DispatcherQueuePriority.Normal);
         }
 
         /// <summary>
@@ -286,19 +289,20 @@ private async void DeviceWatcher_Removed(DeviceWatcher sender, DeviceInformation
             // Protect against race condition if the task runs after the app stopped the deviceWatcher.
             if (sender == _deviceWatcher)
             {
-                await CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
-                {
-                    if (_readerWriterLockSlim.TryEnterWriteLock(TimeSpan.FromSeconds(1)))
+                await _dispatcherQueue.ExecuteOnUIThreadAsync(
+                    () =>
                     {
-                        var device = BluetoothLeDevices.FirstOrDefault(i => i.DeviceInfo.Id == deviceInfoUpdate.Id);
-                        BluetoothLeDevices.Remove(device);
+                        if (_readerWriterLockSlim.TryEnterWriteLock(TimeSpan.FromSeconds(1)))
+                        {
+                            var device = BluetoothLeDevices.FirstOrDefault(i => i.DeviceInfo.Id == deviceInfoUpdate.Id);
+                            BluetoothLeDevices.Remove(device);
 
-                        var unusedDevice = _unusedDevices.FirstOrDefault(i => i.Id == deviceInfoUpdate.Id);
-                        _unusedDevices?.Remove(unusedDevice);
+                            var unusedDevice = _unusedDevices.FirstOrDefault(i => i.Id == deviceInfoUpdate.Id);
+                            _unusedDevices?.Remove(unusedDevice);
 
-                        _readerWriterLockSlim.ExitWriteLock();
-                    }
-                });
+                            _readerWriterLockSlim.ExitWriteLock();
+                        }
+                    }, DispatcherQueuePriority.Normal);
             }
         }
 
@@ -327,16 +331,15 @@ private async Task AddDeviceToList(DeviceInformation deviceInfo)
             // Make sure device name isn't blank or already present in the list.
             if (!string.IsNullOrEmpty(deviceInfo?.Name))
             {
-                var device = new ObservableBluetoothLEDevice(deviceInfo);
+                var device = new ObservableBluetoothLEDevice(deviceInfo, _dispatcherQueue);
                 var connectable = (device.DeviceInfo.Properties.Keys.Contains("System.Devices.Aep.Bluetooth.Le.IsConnectable") &&
                                         (bool)device.DeviceInfo.Properties["System.Devices.Aep.Bluetooth.Le.IsConnectable"]) ||
                                         (device.DeviceInfo.Properties.Keys.Contains("System.Devices.Aep.IsConnected") &&
                                         (bool)device.DeviceInfo.Properties["System.Devices.Aep.IsConnected"]);
 
                 if (connectable)
                 {
-                    await CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(
-                        CoreDispatcherPriority.Normal,
+                    await _dispatcherQueue.ExecuteOnUIThreadAsync(
                         () =>
                         {
                             if (_readerWriterLockSlim.TryEnterWriteLock(TimeSpan.FromSeconds(1)))
@@ -348,7 +351,7 @@ await CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(
 
                                 _readerWriterLockSlim.ExitWriteLock();
                             }
-                        });
+                        }, DispatcherQueuePriority.Normal);
 
                     return;
                 }

Microsoft.Toolkit.Uwp.Connectivity/BluetoothLEHelper/ObservableBluetoothLEDevice.cs

@@ -11,10 +11,11 @@
 using System.Runtime.CompilerServices;
 using System.Threading;
 using System.Threading.Tasks;
-using Windows.ApplicationModel.Core;
+using Microsoft.Toolkit.Uwp.Helpers;
 using Windows.Devices.Bluetooth;
 using Windows.Devices.Bluetooth.GenericAttributeProfile;
 using Windows.Devices.Enumeration;
+using Windows.System;
 using Windows.UI.Core;
 using Windows.UI.Xaml.Media.Imaging;
 
@@ -134,17 +135,22 @@ public int Compare(object x, object y)
         private ObservableCollection<ObservableGattDeviceService> _services =
             new ObservableCollection<ObservableGattDeviceService>();
 
+        private DispatcherQueue _dispatcherQueue;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="ObservableBluetoothLEDevice"/> class.
         /// </summary>
         /// <param name="deviceInfo">The device information.</param>
-        public ObservableBluetoothLEDevice(DeviceInformation deviceInfo)
+        /// <param name="dispatcherQueue">The DispatcherQueue that should be used to dispatch UI updates for this BluetoothLE Device, or null if this is being called from the UI thread.</param>
+        public ObservableBluetoothLEDevice(DeviceInformation deviceInfo, DispatcherQueue dispatcherQueue = null)
         {
             DeviceInfo = deviceInfo;
             Name = DeviceInfo.Name;
 
             IsPaired = DeviceInfo.Pairing.IsPaired;
 
+            _dispatcherQueue = dispatcherQueue ?? DispatcherQueue.GetForCurrentThread();
+
             LoadGlyph();
 
             this.PropertyChanged += ObservableBluetoothLEDevice_PropertyChanged;
@@ -395,7 +401,8 @@ private void ObservableBluetoothLEDevice_PropertyChanged(object sender, Property
         /// <exception cref="Exception">Thorws Exception when no permission to access device</exception>
         public async Task ConnectAsync()
         {
-            await CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(CoreDispatcherPriority.Normal, async () =>
+            await _dispatcherQueue.ExecuteOnUIThreadAsync(
+                async () =>
             {
                 if (BluetoothLEDevice == null)
                 {
@@ -442,7 +449,7 @@ await CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(CoreDispatcherPrio
                         throw new Exception(_result.ProtocolError.GetErrorString());
                     }
                 }
-            });
+            }, DispatcherQueuePriority.Normal);
         }
 
         /// <summary>
@@ -468,8 +475,7 @@ public async Task DoInAppPairingAsync()
         /// <returns>The task of the update.</returns>
         public async Task UpdateAsync(DeviceInformationUpdate deviceUpdate)
         {
-            await CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(
-                CoreDispatcherPriority.Normal,
+            await _dispatcherQueue.ExecuteOnUIThreadAsync(
                 () =>
                 {
                     DeviceInfo.Update(deviceUpdate);
@@ -479,7 +485,7 @@ await CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(
 
                     LoadGlyph();
                     OnPropertyChanged("DeviceInfo");
-                });
+                }, DispatcherQueuePriority.Normal);
         }
 
         /// <summary>
@@ -512,9 +518,7 @@ protected virtual void OnPropertyChanged([CallerMemberName] string propertyName
         /// <param name="args">The arguments.</param>
         private async void BluetoothLEDevice_NameChanged(BluetoothLEDevice sender, object args)
         {
-            await CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(
-                CoreDispatcherPriority.Normal,
-                () => { Name = BluetoothLEDevice.Name; });
+            await _dispatcherQueue.ExecuteOnUIThreadAsync(() => { Name = BluetoothLEDevice.Name; }, DispatcherQueuePriority.Normal);
         }
 
         /// <summary>
@@ -524,29 +528,27 @@ await CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(
         /// <param name="args">The arguments.</param>
         private async void BluetoothLEDevice_ConnectionStatusChanged(BluetoothLEDevice sender, object args)
         {
-            await CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(
-                CoreDispatcherPriority.Normal,
+            await _dispatcherQueue.ExecuteOnUIThreadAsync(
                 () =>
                 {
                     IsPaired = DeviceInfo.Pairing.IsPaired;
                     IsConnected = BluetoothLEDevice.ConnectionStatus == BluetoothConnectionStatus.Connected;
-                });
+                }, DispatcherQueuePriority.Normal);
         }
 
         /// <summary>
         /// Load the glyph for this device
         /// </summary>
         private async void LoadGlyph()
         {
-            await CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(
-                CoreDispatcherPriority.Normal,
+            await _dispatcherQueue.ExecuteOnUIThreadAsync(
                 async () =>
                 {
                     var deviceThumbnail = await DeviceInfo.GetGlyphThumbnailAsync();
                     var glyphBitmapImage = new BitmapImage();
                     await glyphBitmapImage.SetSourceAsync(deviceThumbnail);
                     Glyph = glyphBitmapImage;
-                });
+                }, DispatcherQueuePriority.Normal);
         }
     }
 }

Microsoft.Toolkit.Uwp.Connectivity/BluetoothLEHelper/ObservableGattCharacteristics.cs

@@ -7,10 +7,12 @@
 using System.Linq;
 using System.Runtime.CompilerServices;
 using System.Threading.Tasks;
+using Microsoft.Toolkit.Uwp.Helpers;
 using Windows.Devices.Bluetooth;
 using Windows.Devices.Bluetooth.GenericAttributeProfile;
 using Windows.Security.Cryptography;
 using Windows.Storage.Streams;
+using Windows.System;
 
 namespace Microsoft.Toolkit.Uwp.Connectivity
 {
@@ -110,13 +112,17 @@ public enum DisplayTypes
         /// </summary>
         private string _value;
 
+        private DispatcherQueue _dispatcherQueue;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="ObservableGattCharacteristics"/> class.
         /// </summary>
         /// <param name="characteristic">The characteristic.</param>
         /// <param name="parent">The parent.</param>
         public ObservableGattCharacteristics(GattCharacteristic characteristic, ObservableGattDeviceService parent)
         {
+            _dispatcherQueue = DispatcherQueue.GetForCurrentThread();
+
             Characteristic = characteristic;
             Parent = parent;
             Name = GattUuidsService.ConvertUuidToName(Characteristic.Uuid);
@@ -459,9 +465,7 @@ protected virtual void OnPropertyChanged([CallerMemberName] string propertyName
         /// <param name="args">The <see cref="GattValueChangedEventArgs"/> instance containing the event data.</param>
         private async void Characteristic_ValueChanged(GattCharacteristic sender, GattValueChangedEventArgs args)
         {
-            await Windows.ApplicationModel.Core.CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(
-                Windows.UI.Core.CoreDispatcherPriority.Normal,
-                () => { SetValue(args.CharacteristicValue); });
+            await _dispatcherQueue.ExecuteOnUIThreadAsync(() => { SetValue(args.CharacteristicValue); }, DispatcherQueuePriority.Normal);
         }
 
         /// <summary>

Microsoft.Toolkit.Uwp.SampleApp/Controls/CodeRenderer.cs

@@ -87,10 +87,14 @@ protected override void OnApplyTemplate()
 
         private void RenderDocument()
         {
-            _codeView?.Blocks?.Clear();
-            _formatter = new RichTextBlockFormatter(_theme);
-            _formatter.FormatRichTextBlock(_displayedText, _language, _codeView);
-            _rendered = true;
+            if (_codeView != null)
+            {
+                _codeView.Blocks?.Clear();
+                _formatter = new RichTextBlockFormatter(_theme);
+
+                _formatter.FormatRichTextBlock(_displayedText, _language, _codeView);
+                _rendered = true;
+            }
         }
 
         private void CopyButton_Click(object sender, RoutedEventArgs e)

Microsoft.Toolkit.Uwp.SampleApp/Shell.xaml.cs

@@ -6,6 +6,7 @@
 using Microsoft.Toolkit.Uwp.Helpers;
 using Microsoft.Toolkit.Uwp.SampleApp.Pages;
 using Microsoft.Toolkit.Uwp.UI.Extensions;
+using Windows.System;
 using Windows.UI.Xaml;
 using Windows.UI.Xaml.Controls;
 using Windows.UI.Xaml.Media.Animation;
@@ -127,7 +128,7 @@ private void SamplePickerGridView_Loaded(object sender, Windows.UI.Xaml.RoutedEv
             {
                 if (s is UIElement samplePicker && samplePicker.Visibility == Visibility.Visible)
                 {
-                    DispatcherHelper.ExecuteOnUIThreadAsync(() => SamplePickerGridView.Focus(FocusState.Keyboard));
+                    DispatcherQueue.GetForCurrentThread().ExecuteOnUIThreadAsync(() => SamplePickerGridView.Focus(FocusState.Keyboard));
                 }
             });
         }

Microsoft.Toolkit.Uwp.UI/Cache/ImageCache.cs

@@ -10,6 +10,7 @@
 using Microsoft.Toolkit.Uwp.Helpers;
 using Windows.Storage;
 using Windows.Storage.Streams;
+using Windows.System;
 using Windows.UI.Xaml.Media.Imaging;
 
 namespace Microsoft.Toolkit.Uwp.UI
@@ -34,11 +35,14 @@ public class ImageCache : CacheBase<BitmapImage>
         /// </summary>
         public static ImageCache Instance => _instance ?? (_instance = new ImageCache());
 
+        private DispatcherQueue _dispatcherQueue;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="ImageCache"/> class.
         /// </summary>
         public ImageCache()
         {
+            _dispatcherQueue = DispatcherQueue.GetForCurrentThread();
             _extendedPropertyNames.Add(DateAccessedProperty);
         }
 
@@ -55,7 +59,7 @@ protected override async Task<BitmapImage> InitializeTypeAsync(Stream stream, Li
                 throw new FileNotFoundException();
             }
 
-            return await DispatcherHelper.ExecuteOnUIThreadAsync(async () =>
+            return await _dispatcherQueue.ExecuteOnUIThreadAsync(async () =>
             {
                 BitmapImage image = new BitmapImage();