Work on serial device detection

USB Test App WPF/App.xaml.cs

@@ -23,13 +23,19 @@ public App()
         {
             Activated += App_Activated;
             Deactivated += App_Deactivated;
-
+            Exit += App_Exit;
             vml = new ViewModelLocator();
 
             var serialClient = CreateSerialDebugClient();
             ServiceLocator.Current.GetInstance<MainViewModel>().SerialDebugService = serialClient;
         }
 
+        private void App_Exit(object sender, System.Windows.ExitEventArgs e)
+        {
+            var serialClient = ServiceLocator.Current.GetInstance<MainViewModel>().SerialDebugService;
+            serialClient.SerialDebugClient.StopDeviceWatchers();
+        }
+
         private void App_Deactivated(object sender, EventArgs e)
         {
             //throw new NotImplementedException();

USB Test App WPF/MainWindow.xaml.cs

@@ -116,7 +116,7 @@ private void ConnectDeviceButton_Click(object sender, RoutedEventArgs e)
                 device.CreateDebugEngine(NanoSerialDevice.SafeDefaultTimeout);
             }
 
-            bool connectResult = device.DebugEngine.Connect(5000, true);
+            bool connectResult = device.DebugEngine.Connect(5000, true, true);
 
             if(connectResult)
             {

nanoFramework.Tools.DebugLibrary.Shared/PortSerial/DeviceWatcher.cs

@@ -11,10 +11,11 @@
 
 namespace nanoFramework.Tools.Debugger.PortSerial
 {
-    public class DeviceWatcher
+    public class DeviceWatcher : IDisposable
     {
         private bool _started = false;
         private List<string> _ports;
+        private Thread _threadWatch = null;
 
         public delegate void EventDeviceAdded(object sender, string port);
 
@@ -30,14 +31,14 @@ public void Start()
         {
             if (!_started)
             {
-                var threadWatch = new Thread(() =>
+                _threadWatch = new Thread(() =>
                 {
                     _ports = new List<string>();
 
                     _started = true;
 
                     Status = DeviceWatcherStatus.Started;
-                    
+
                     while (_started)
                     {
                         var ports = GetPortNames();
@@ -81,7 +82,7 @@ public void Start()
                 {
                     Priority = ThreadPriority.Lowest
                 };
-                threadWatch.Start();
+                _threadWatch.Start();
             }
         }
 
@@ -109,9 +110,9 @@ private List<string> GetPortNames()
                                 // If the device is still plugged, it should appear as valid here, if not present, it means, the device has been disconnected
                                 string portDescription = (string)activePorts.GetValue($"{portNameDetails.Groups[2]}");
                                 int numPorts = (int)activePorts.GetValue("Count");
-                                if((portDescription == null) && (numPorts > 0))
+                                if ((portDescription == null) && (numPorts > 0))
                                 {
-                                    portDescription = (string)activePorts.GetValue($"{numPorts - 1}"); 
+                                    portDescription = (string)activePorts.GetValue($"{numPorts - 1}");
                                 }
 
                                 if (portDescription != null)
@@ -176,5 +177,17 @@ public void Stop()
             _started = false;
             Status = DeviceWatcherStatus.Stopping;
         }
+
+        public void Dispose()
+        {
+            Stop();
+
+            while (Status != DeviceWatcherStatus.Started)
+            {
+                Thread.Sleep(50);
+            }
+
+            _threadWatch = null;
+        }
     }
 }

nanoFramework.Tools.DebugLibrary.Shared/PortSerial/PortSerialManager.cs

@@ -161,12 +161,7 @@ private void StopDeviceWatchersInternal()
                 NanoFrameworkDevices.Remove(device);
 
                 device?.DebugEngine?.StopProcessing();
-                device?.DebugEngine?.Dispose();
-
-                device?.Disconnect();
-
-                // This closes the handle to the device
-                ((NanoDevice<NanoSerialDevice>)device)?.Dispose();
+                device?.DebugEngine?.Stop(true);
             }
 
             _watchersStarted = false;