Question

My Silverlight 4 application keeps in contact with a server side through a wcf service. Whenever the user refreshes, navigates away or terminates the browser I should do some cleanup towards the server side.

I can not use the Application Exit event; my wcf client is dead before it eventually gets called. I can not use the (new in SL4) FrameworkElement Unloaded event; it ain’t called when the Silverlight app shuts down.

So, how do I detect the browser refresh, newpage or shutdown in time to do my cleanup?

Answer 1

BaBu,

I do this exact thing when a user navigates away from my Silverlight app (or does a refresh). Follow the steps below to catch this event.

1.) Start by listening for the HTML page’s “onbeforeunload” event, like so…

public void Application_Startup(object sender, StartupEventArgs e)
{
    bool ok = HtmlPage.Window.AttachEvent("onbeforeunload", Application_BeforeExit);
    ok = HtmlPage.Document.AttachEvent("onbeforeunload", Application_BeforeExit);
    MainPage mainPage = new MainPage();
    base.RootVisual = mainPage;
}

2.) Implement Application_BeforeExit() to setup and call an ASP.NET “PageMethod”, like so…

private void Application_BeforeExit(object sender, HtmlEventArgs args)
{
    string methodName = "ModelShutdown";
    params object[] args = new Guid().ToString());;

    try
    {
        ScriptObject pageMethods = (ScriptObject)HtmlPage.Window.GetProperty("PageMethods");
        if (pageMethods == null)
            throw new ArgumentException("Web page does not support PageMethods");
        object[] pageMethodArgs = { new PageMethodEventHandler(Success), new PageMethodEventHandler(Failure), null/*userContext*/};
        object[] combinedArgs = new object[args.Length + pageMethodArgs.Length];
        args.CopyTo(combinedArgs, 0);
        pageMethodArgs.CopyTo(combinedArgs, args.Length);
        pageMethods.Invoke(methodName, combinedArgs);
    }
    catch (Exception ex)
    {
        //ex.Alert();
    }
}

3.) Add the PageMethod to your page code behind (Index.aspx.cs), like so,

public partial class Index : Page
{
    [WebMethod] // a PageMethod called from Silverlight
    public static void ModelShutdown(string identifier)
    {
        System.Diagnostics.Debug.WriteLine("*** Signing Off: " + identifier);
    }
}

4.) Allow PageMethods on your page (Indx.aspx), like so,

<asp:ScriptManager runat="server" EnablePageMethods="true" />
<div id="silverlightControlHost">
    <object data="data:application/x-silverlight-2," type="application/x-silverlight-2" width="100%" height="100%">

Good luck,
Jim McCurdy, YinYangMoney.com