Hi. We have an issue in our Silverlight application which uses WCF and Entity Framework, where we need to trap the event whenever a user shuts down the application by closing the web page or the browser instead of closing the silverlight application. This is in order to verify if any changes have been made, in which case we would ask the user if he wants to save before leaving. We were able to accomplish the part which consists in trapping the closing of the web page: we wrote some code in the application object that have the web page call a method in the silverlight application object. The problem starts when in this method, we do an asynchroneous call to the Web Service to verify if changes have occured (IsDirty). We are using a DispatcherTimer to check for the return of the asynchroneous call. The problem is that the asynchroneous call never completes (in debug mode, it never ends up stepping into the _BfrServ_Customer_IsDirtyCompleted method), while it used to work fine before we added this new functionality. You will find belowthe code we are using. I am new to writing timers in combination with asynchroneous call so I may be doing something wrong but I cannot figure out what. I tried other things also but we without any success.. ====================== CODE ============================================== 'Code in the application object Public Sub New() InitializeComponent() RegisterOnBeforeUnload() _DispatcherTimer.Interval = New TimeSpan(0, 0, 0, 0, 500) End Sub Public Sub RegisterOnBeforeUnload() 'Register Silverlight object for availability in Javascript. Const scriptableObjectName As String = "Bridge" HtmlPage.RegisterScriptableObject(scriptableObjectName, Me) 'Start listening to Javascript event. Dim pluginName As String = HtmlPage.Plugin.Id HtmlPage.Window.Eval(String.Format("window.onbeforeunload = function () {{ var slApp = document.getElementById('{0}'); var result = slApp.Content.{1}.OnBeforeUnload(); if(result.length 0)return result;}}", pluginName, scriptableObjectName)) End Sub Public Function OnBeforeUnload() As String Dim userControls As List(Of UserControl) = New List(Of UserControl) Dim test As Boolean = True If CType(Me.RootVisual, StartPage).LayoutRoot.Children.Item(0).GetType().Name = "MainPage" Then If Not CType(CType(Me.RootVisual, StartPage).LayoutRoot.Children.Item(0), MainPage).FindName("Tab") Is Nothing Then If CType(CType(Me.RootVisual, StartPage).LayoutRoot.Children.Item(0), MainPage).FindName("Tab").Items.Count = 1 Then For Each item As TabItem In CType(CType(Me.RootVisual, StartPage).LayoutRoot.Children.Item(0), MainPage).Tab.Items If item.Content.GetType().Name = "CustomerDetailUI" _Item = item WaitHandle = New AutoResetEvent(False) DoAsyncCall() Exit End If Next End If End If End If If _IsDirty = True Then Return "Do you want to save before leaving." Else Return String.Empty End If End Function Private Sub DoAsyncCall() _Item.Content.CheckForIsDirty(WaitHandle) 'This code resides in the CustomerDetailUI UserControl - see below for the code End Sub Private Sub _DispatcherTimer_Tick(ByVal sender As Object, ByVal e As System.EventArgs) Handles _DispatcherTimer.Tick If Not _Item.Content._IsDirtyCompleted = True Then Exit Sub End If _DispatcherTimerRunning = False _DispatcherTimer.Stop() ProcessAsyncCallResult() End Sub Private Sub ProcessAsyncCallResult() _IsDirty = _Item.Content._IsDirty End Sub 'CustomerDetailUI code Public Sub CheckForIsDirty(ByVal myAutoResetEvent As AutoResetEvent) _AutoResetEvent = myAutoResetEvent _BfrServ.Customer_IsDirtyAsync(_Customer) 'This method initiates asynchroneous call to the web service - all the details are not shown here _AutoResetEvent.WaitOne() End Sub Private Sub _BfrServ_Customer_IsDirtyCompleted(ByVal sender As Object, ByVal e As BFRService.Customer_IsDirtyCompletedEventArgs) Handles _BfrServ.Customer_IsDirtyCompleted If _IsDirtyFromRefesh Then _IsDirtyFromRefesh = False If e.Result = True Then Me.Confirm("This customer has been modified. Are you sure you want to refresh your data ? " & vbNewLine & " Your changes will be lost.", "Yes", "No", Message.CheckIsDirtyRefresh) End If Busy.IsBusy = False Else If e.Result = True Then _IsDirty = True Me.Confirm("This customer has been modified. Would you like to save?", "Yes", "No", Message.CheckIsDirty) Else Me.Tab.Items.Remove(Me.Tab.SelectedItem) Busy.IsBusy = False End If End If _IsDirtyCompleted = True _AutoResetEvent.Set() End Sub