title: How to find if child window is opened or not
body: <p>I have a requirement where I need to check whether any records have changed, depending on that I need to alert user. 
  So using timer for every 5 sec I am trying to verify from database and showing alert window to the user. working great.</p>
  
  <p>the problem is that, if the user stays idle for a long time. I am getting multiple alert windows as time pass on.(considering data changes for every 2 sec).</p>
  
  <p>So I need to know if the alert window is already opened, How can get the instance of the opened window where I can either do some operation on it.</p>
  
  <p>Here I don't want to create any single instance. Please let me know if there is any way directly can be done in silverlight.</p>