private async void DeviceWatcher_Removed(DeviceWatcher sender, DeviceInformationUpdate deviceInfoUpdate)
        {
            // We must update the collection on the UI thread because the collection is databound to a UI element.
            await Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
            {
                lock (this)
                {
                    Debug.WriteLine(String.Format("Removed {0}{1}", deviceInfoUpdate.Id, ""));

                    // Protect against race condition if the task runs after the app stopped the deviceWatcher.
                    if (sender == deviceWatcher)
                    {
                        // Find the corresponding DeviceInformation in the collection and remove it.
                        BluetoothLEDeviceDisplay bleDeviceDisplay = FindBluetoothLEDeviceDisplay(deviceInfoUpdate.Id);
                        if (bleDeviceDisplay != null)
                        {
                            KnownDevices.Remove(bleDeviceDisplay);
                        }

                        DeviceInformation deviceInfo = FindUnknownDevices(deviceInfoUpdate.Id);
                        if (deviceInfo != null)
                        {
                            UnknownDevices.Remove(deviceInfo);
                        }
                    }
                }
            });
        }
        private async void DeviceWatcher_Updated(DeviceWatcher sender, DeviceInformationUpdate deviceInfoUpdate)
        {
            // We must update the collection on the UI thread because the collection is databound to a UI element.
            await Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
            {
                lock (this)
                {
                    Debug.WriteLine(String.Format("Updated {0}{1}", deviceInfoUpdate.Id, ""));

                    // Protect against race condition if the task runs after the app stopped the deviceWatcher.
                    if (sender == deviceWatcher)
                    {
                        BluetoothLEDeviceDisplay bleDeviceDisplay = FindBluetoothLEDeviceDisplay(deviceInfoUpdate.Id);
                        if (bleDeviceDisplay != null)
                        {
                            // Device is already being displayed - update UX.
                            bleDeviceDisplay.Update(deviceInfoUpdate);
                            return;
                        }

                        DeviceInformation deviceInfo = FindUnknownDevices(deviceInfoUpdate.Id);
                        if (deviceInfo != null)
                        {
                            deviceInfo.Update(deviceInfoUpdate);
                            // If device has been updated with a friendly name it's no longer unknown.
                            if (deviceInfo.Name != String.Empty)
                            {
                                KnownDevices.Add(new BluetoothLEDeviceDisplay(deviceInfo));
                                UnknownDevices.Remove(deviceInfo);
                            }
                        }
                    }
                }
            });
        }