How to use a timer to display content?

I am having issues with getting my timer to change content on a window.

I initialize my timer by:

timeOutTimer = new System.Timers.Timer(15000);
            timeOutTimer.Ela开发者_如何学Pythonpsed += new ElapsedEventHandler(timeOutEvent);
            timeOutTimer.Enabled = true;
            timeOutTimer.AutoReset = false;
            timeOutTimer.Start();

I have a ContentControl which is Hidden.

When the timer passes 15 seconds it should change the visibility of the ContentControl

private void timeOutEvent(object sender, ElapsedEventArgs e)
{
    TicketContent.Visibility = Visibility.Visible;
    Console.WriteLine("TIMED OUT");
    timeOutTimer.Stop();

}

I am getting an exception : System.InvalidOperationException

What am I doing wrong?

Thanks in advance!

Why not use DispatcherTimer

timer = new DispatcherTimer(
    TimeSpan.FromSeconds(15), 
    DispatcherPriority.Background, 
    TimeoutEvent, 
    this.Dispatcher);

timer.Start();

When you start a timer, it begins on a separate non UI thread. As it is in a separate thread it cannot access elements in the UI thread. A delegate in combination with a Dispatcher.BeginInvoke() method will allow you to modify the properties of UI elements.

    private void timeOutEvent(object sender, ElapsedEventArgs e)
    {
        TicketContent.Dispatcher.BeginInvoke(DispatcherPriority.Normal, new InvokeDelegate(TimeOutEvent));
        Console.WriteLine("TIMED OUT");
        timeOutTimer.Stop();
    }

    public delegate void InvokeDelegate();


    private void TimeOutEvent()
    {
        TicketContent.Visibility = Visibility.Visible;
    }