How to change label content with timers throwing InvalidOperationException

Question

I'm making an application and I'm using a timer in that application to change label content in WPF C# .NET.

In the timer's elapsed event I'm writing the following code

lblTimer.Content = "hello";

but its throwing an InvalidOperationException and gives a message The calling thread cannot access this object because a different thread owns it.

I'm using .NET framework 3.5 and WPF with C#.

Please help me.
Thanks in advance.

What timer are you using? Specifically, what is the namespace of your timer? .NET provides at least 3 AFAIK. — leppie, Apr 26 '10 at 07:06

score 11 · Answer 1 · answered May 21 '12 at 20:00

For .NET 4.0 it is much simpler to use a DispatcherTimer. The eventhandler is then in the UI thread and it can set properties of the control directly.

private DispatcherTimer updateTimer;

private void initTimer
{
     updateTimer = new DispatcherTimer(DispatcherPriority.SystemIdle); 
     updateTimer.Tick += new EventHandler(OnUpdateTimerTick);
     updateTimer.Interval = TimeSpan.FromMilliseconds(1000);
     updateTimer.Start();
}

private void OnUpdateTimerTick(object sender, EventArgs e)
{
    lblTimer.Content = "hello";
}

score 1 · Answer 2 · answered Apr 26 '10 at 07:30

InvokeRequired doesn't work in wpf.

The proper way the update a GUI element owned by another thread is this :

Declare this on module level :

delegate void updateLabelCallback(string tekst);

This is the method to update your label :

private void UpdateLabel(string tekst)
    {
        if (label.Dispatcher.CheckAccess() == false)
        {
            updateLabelCallback uCallBack = new updateLabelCallback(UpdateLabel);
            this.Dispatcher.Invoke(uCallBack, tekst);
        }
        else
        { 
    //update your label here
        }
     }

How to change label content with timers throwing InvalidOperationException

2 Answers2