Question

I am trying to have a label display the time it takes the user to complete a task which starts at 00:00:00 and goes up in shown millisecond increments from there.
So far I have this:

    private void startTimer()
    {
        stopWatch.Start();
        Dispatcher.BeginInvoke(DispatcherPriority.Render, new ThreadStart(ShowElapsedTime));
    }
    void ShowElapsedTime()
    {
        TimeSpan ts = stopWatch.Elapsed;
        lblTime.Text = String.Format("{0:00}:{1:00}.{2:00}", ts.Minutes, ts.Seconds, ts.Milliseconds / 10);
    }

startTimer(); is called on a button click

Can someone point me in the right direction?

Answer 1

I’d recommend taking an MVVM approach. Have your TextBlock bind to a string member on your ViewModel. In your ViewModel you can use a DispatcherTimer to set the the time elapsed. The DispatcherTimer fires its callback on the UI thread so you don’t need to invoke to the UI thread.

Code:

public class ViewModel : INotifyPropertyChanged
{
     public event PropertyChangedEventHandler PropertyChanged;
     public string TimeElapsed {get;set;}

     private DispatcherTimer timer;
     private Stopwatch stopWatch;

     public void StartTimer()
     {
          timer = new DispatcherTimer();
          timer.Tick += dispatcherTimerTick_;
          timer.Interval = new TimeSpan(0,0,0,0,1);
          stopWatch = new Stopwatch();
          stopWatch.Start();
          timer.Start();
     }



     private void dispatcherTimerTick_(object sender, EventArgs e)
     {
         TimeElapsed = stopWatch.Elapsed.TotalMilliseconds; // Format as you wish
         PropertyChanged(this, new PropertyChangedEventArgs("TimeElapsed")); 
     }
}

XAML:

<TextBlock Text="{Binding TimeElapsed}"/>