WPF MVVM update label text

My label text isn't updating properly in my 3.5 WPF MVVM app. The do work part lasts long enough that you can see the waiting mouse pointer. All I ever see is "Parsed" in the label, which is Bound to InfoText. the Dispatcher and do work lines are in a Command's method. Ideas?

The code

Dispatcher.Invoke((Action<string>)SetInfoText, "Start Parsing");
//do work
 Dispatcher.Invoke((Acti开发者_JAVA技巧on<string>)SetInfoText, "Parsed");

 private void SetInfoText(string text)
    {
        InfoText = text;
    }

  private string _infoText;
    public string InfoText
    {
        get
        {
            return _infoText;
        }
        set
        {
            _infoText = value;
            OnPropertyChanged("InfoText");
        }
    }

The only thing I can think of to explain it is that you're doing the work on the UI thread. This would prevent the dispatcher from redrawing until your work is done. The work being passed in Invoke is placed in the event queue, meaning it will be performed when idle.

The proper way to fix it is to do the work on a separate thread. If you're looking for workarounds though, look here. Reference: MSDN

EDIT: There are lots of ways to perform the work on another thread. Read up on BackgroundWorker, ThreadPool, Task Parallell Library, Threads. :) Here's a really simple way to do the work in a background thread:

     System.Threading.ThreadPool.QueueUserWorkItem( state => 
     {
        Dispatcher.Invoke((Action<string>)SetInfoText, "Start Parsing");
        System.Threading.Thread.Sleep(5000); // Simulate work
        Dispatcher.Invoke((Action<string>)SetInfoText, "Parsed");
     });

 Application.Current.Dispatcher.BeginInvoke(new Action(() => this.InfoText="Start Parsing"));

this works for me.

nevertheless i would put my long running process in a backgroundworker. so ui thread will not get blocked.

edit: if you do all your work in ui thread you should look at the overload for BeginInvoke - you can pass a DispatcherPriority. may be this helps too