title: How to use a timer to display content?
body: <p>I am having issues with getting my timer to change content on a window.</p>
  
  <p>I initialize my timer by:</p>
  
  <pre><code>timeOutTimer = new System.Timers.Timer(15000);
              timeOutTimer.Elapsed += new ElapsedEventHandler(timeOutEvent);
              timeOutTimer.Enabled = true;
              timeOutTimer.AutoReset = false;
              timeOutTimer.Start();
  </code></pre>
  
  <p>I have a ContentControl which is Hidden.</p>
  
  <p>When the timer passes 15 seconds it should change the visibility of the ContentControl</p>
  
  <pre><code>private void timeOutEvent(object sender, ElapsedEventArgs e)
  {
      TicketContent.Visibility = Visibility.Visible;
      Console.WriteLine("TIMED OUT");
      timeOutTimer.Stop();
  
  }
  </code></pre>
  
  <p>I am getting an exception :
  System.InvalidOperationException</p>
  
  <p>What am I doing wrong?</p>
  
  <p>Thanks in advance!</p>