从另一个线程异步更新wpf UI

Question

I have a WPF UI and I want to update it asynchronously from another thread by calling some events.

I know how to call events and invoke them in UI Thread, but I want to do it async.

public partial class HomeUI 
{
    public HomeUI()
    {
        var test = new LogicClass();
        test.UI_StartPlaying += StartPlaying;

        new Thread(test.Start).Start();
    }

    private void StartPlaying(object sender, EventArgs e)
    {
        Dispatcher.Invoke(new Action(() =>
        {
            var streamAddress = (e as UIUpdateEventArgs).StreamAddress;
            vlc.Stop();
            vlc.Media = new LocationMedia(streamAddress);
            vlc.Play();
        }));
    }

}


public class LogicClass
{
    public event EventHandler UI_StartPlaying;
    public void Start()
    {
        DoSomethings();
        UI_StartPlaying(this, new UIUpdateEventArgs(streamAddress));
        DoSomethingElse();
    }
}

class UIUpdateEventArgs : EventArgs
{
    string StreamAddress {get; set;}
    public UIUpdateEventArgs( string streamAddress)
    {
        this.StreamNumber = streamNumber;
    }
}

but in this code, when something happening in DoSomethingElse() part that cause delay or stop the logic thread, UI freezes.
Edit: in DoSomethingElse() part, I run 2 Threads that one of them do all the DB transactions and have some delay. this delay, make the vlc pause (freeze on a random frame) on the UI and then make the whole UI freeze.
Obviously, when I comment these transactions, program work properly.
What should I do to make the UIEventUpdate run asynchronously with my Logic Thread ?

Answer 1

You can use Dispatcher.BeginInvoke to get what you need. This function is returning directly, the delegate gets scheduled and called later.

If your requirement is that DoSomethingElse() is called after StartPlaying finished, you have to await the Dispatcher.BeginInvoke call.

I don´t know about LocationMedia but if new LocationMedia(streamAddress); is an expensive creation (takes long and/or needs lot of memory) i would do it outside the Dispatcher delegate if possible.

var streamAddress = (e as UIUpdateEventArgs).StreamAddress;
var media = new LocationMedia(streamAddress);
Dispatcher.BeginInvoke(new Action(() =>
{
    vlc.Stop();
    vlc.Media = media;
    vlc.Play();
}));

Greetings!

Answer 2

Use Dispatcher.InvokeAsync Method instead of Invoke method. MSDN Link