Lync SDK . Issue with Multiple UI threads

Question

I'm seeing an issue where having multiple UI threads with Lync 2010 SDK controls are causing the program to crash.

The error I'm running into is:

{"Must create DependencySource on same Thread as the DependencyObject."}

If someone can give me an explanation as to why this happens ,or how to get around this. It will be great!

<Window x:Class="Lync.MainWindow"
            xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
            xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
            xmlns:lync="clr-namespace:Microsoft.Lync.Controls;assembly=Microsoft.Lync.Controls"
            Title="MainWindow" Height="350" Width="525">
        <StackPanel>
            <lync:PresenceIndicator Source="sip:gawicks@home.com"/>
            <Button Height="20" Width="20"  Click="Button_Click"> </Button>        
        </StackPanel>
    </Window>



  private void Button_Click(object sender, RoutedEventArgs e)
        {
            //Simply creating another UI thread on button click https://eprystupa.wordpress.com/2008/07/28/running-wpf-application-with-multiple-ui-threads/
            Thread thread = new Thread(() =>
            {

                MainWindow w = new MainWindow();
                //Crash!!
                w.Show();

                w.Closed += (sender2, e2) =>
                 w.Dispatcher.InvokeShutdown();

                System.Windows.Threading.Dispatcher.Run();
            });

            thread.SetApartmentState(ApartmentState.STA);
            thread.Start();

        }

The issue has nothing to do with LYNC, rather it's an issue with attempting to spin up a new GUI on some thread other than the thread the current window is running. Get rid of your Thread logic and you'll be ok. — JWP, Dec 28 '15 at 05:24
The requirement IS to run on a new thread. Which should work https://eprystupa.wordpress.com/2008/07/28/running-wpf-application-with-multiple-ui-threads/. All other controls work fine. I can confirm that the lync control is causing the problem. — gawicks, Dec 28 '15 at 05:28
Try setting thread.IsBackground = true after setting the ApartmentState — William, Dec 28 '15 at 05:29
Ok. One other thing you can try is setting the SynchronizationContext (in the thread start, before the main window initialization) like so: `SynchronizationContext.SetSynchronizationContext( new DispatcherSynchronizationContext( Dispatcher.CurrentDispatcher));` — William, Dec 28 '15 at 05:34
The Lync client SDK is kind of garbage. It has some serious issues with threading. It'd be nice if Microsoft would ever get around to an update - but as it is, it is easier to build your own UI elements that interact with a decently multi-threaded UCMA or UCWA backend if that is at all possible. — EricRRichards, Aug 31 '16 at 14:01

score 1 · Accepted Answer · answered Mar 20 '16 at 06:09

Seems like this is indeed a limitation of the Lync controls. Internally these controls use the Lync client. And the lync client being a COM wrapper likes to live on a single UI thread.

So instead I came up with my own control. Wrote a facade over the lync client which lives on a single UI thread. And Dispatched all calls to it. And Voilà its working!

score 0 · Answer 2 · answered Dec 28 '15 at 05:37

0

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        //Simply creating another UI thread on button click https://eprystupa.wordpress.com/2008/07/28/running-wpf-application-with-multiple-ui-threads/
        Thread thread = new Thread(() =>
        {
            SynchronizationContext.SetSynchronizationContext(
            new DispatcherSynchronizationContext(
            Dispatcher.CurrentDispatcher));

            MainWindow w = new MainWindow();
            //Crash!!
            w.Show();

            w.Closed += (sender2, e2) =>
            w.Dispatcher.InvokeShutdown();

            System.Windows.Threading.Dispatcher.Run();
        });

        thread.SetApartmentState(ApartmentState.STA);
        thread.Start();

    }

Try setting the SynchronizationContext of the newly created thread as shown above.

answered Dec 28 '15 at 05:37

William

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What is happening in the constructor for `MainWindow`? If you strip it down to `InitializeComponent` does it still throw the error? – William Dec 28 '15 at 05:40
Yes ive got zero logic in there except InitializeComponent(). – gawicks Dec 28 '15 at 05:42
And just out of curiosity if you remove this line from the xaml `` does it still throw the error?. If it doesn't then it does indeed look like it's to do with LYNC – William Dec 28 '15 at 05:45
edit : sorry I meant that the error goes away if is removed. So I'm fairly confident this is lync specific. – gawicks Dec 28 '15 at 05:45

JWP · Answer 3 · 2015-12-29T01:49:30.417

0

None of the solutions given here will work if Lync itself dissallows more than a singleton instance of Lync. If I recall, this is the case as the designers wanted it that way. Lync simply will not start twice.

edited Dec 29 '15 at 01:49

answered Dec 28 '15 at 05:41

JWP

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yes Im aware. There are several equivalent approaches to creating a WPF UI thread . The question is rather , why the lync sdk behaves erratically in this situation. – gawicks Dec 28 '15 at 05:47
Ok, but the code above doesn't show the starting of the dispatcher on the new thread, per Reed's article. Can you try that? – JWP Dec 28 '15 at 05:56
Maybe we were misunderstanding the issue a bit, does the exception happen in the button click logic or when the mainwindow is shown prior to the button click? – JWP Dec 28 '15 at 05:57
The button click logic fires off a new UI thread. It's here that the exception happens. – gawicks Dec 28 '15 at 05:59

Lync SDK . Issue with Multiple UI threads

3 Answers3