clear clipboard when timer timeouts

Question

I am using a timer as

System.Threading.Timer clipboardTimer = new Timer(ClearClipboard);

Next, I change its interval as

clipboardTimer.Change(1000, 30000);

In the handle timeout function, i.e. ClearClipboard, I want to clear the clipboard as

void ClearClipboard(object o)
{
    Clipboard.SetText("");
}

but there is System.Unauthorised exception. Maybe, this is because there are two different threads. So, how can I invoke clear clipboard efficiently?

Answer 1

This error occurs because the Timer event fires on a separate thread than the UI thread. You can change a UI element in one of two ways. The first is to tell the Dispatcher object to execute the code on the UI thread. If your object with the Timer is a DependencyObject (e.g. PhoneApplicationPage), you can use the Dispatcher property. This is done with the BeginInvoke method.

void ClearClipboard(object o)
{
    Dispatcher.BeginInvoke(() => Clipboard.SetText(""));
}

If your object is not a DependencyObject, you can use the Deployment object to access the Dispatcher.

void ClearClipboard(object o)
{
    Deployment.Current.Dispatcher.BeginInvoke(() => Clipboard.SetText(""));
}

The second option is to use the DispatcherTimer instead of the Timer. The DispatcherTimer event does fire on the UI Thread!

// Create the timer
DispatcherTimer timer = new DispatcherTimer();
timer.Interval = TimeSpan.FromSeconds(3);
timer.Tick += TimerOnTick;

// The subscription method
private void TimerOnTick(object sender, EventArgs eventArgs)
{
    Clipboard.SetText("");
}