Question

Possible Duplicate:
How to update GUI from another thread in C#?
My Timer event crashes because the events are called on a different thread

I have a timer object that I want to periodically update a UI control which is a label. However it crashes and says I need to update it on the UI thread. Can anyone help?

private void frmMain_Load(object sender, EventArgs e)
    {
        aTimer = new System.Timers.Timer(1000);          
        aTimer.Elapsed += new ElapsedEventHandler(OnTimedEvent);
        aTimer.Interval = 2000;
        aTimer.Enabled = true;
   }
   public void updateUI()
    {

        lblAirTrack.Text = "Tracking: " + itemList.Count + " items";

    }

Answer 1

If you’re using .NET 3.5+, use the dispatcher. Otherwise something like this should work:

private delegate void updateUIDelegate();

public void updateUI()
{
    if (lblAirTrack.InvokeRequired)
    {
        lblAirTrack.Invoke(new updateUIDelegate(updateUI));
    }
    else
    {
        lblAirTrack.Text = "Tracking: " + itemList.Count + " items";
    }
}