title: WPF send event from App to User control
body: <p>In my application, I use an event to check network status. In the MainWindow, I instantiate some user controls (for example, I have 3 child user controls), and in one of these child controls, I need to catch the event from the App to this specific user control. </p>
  
  <p>In the App I use this to start: </p>
  
  <pre><code>protected override void OnStartup(StartupEventArgs e)
  {
      NetworkStatus.AvailabilityChanged +=
         new NetworkStatusChangedHandler(DoAvailabilityChanged);
      base.OnStartup(e);
  }
  
  static void DoAvailabilityChanged(
       object sender, NetworkStatusChangedArgs e)
          {
               //this method will send a notification
              //ReportAvailability();
          }
  </code></pre>
  
  <p>When I catch this event, I need to change the brushes in my StackPanel. After I have created the two brushes, how I can change them? I have seen some information about custom triggers. How can I use those in my StackPanel?</p>