title: Property Metadata is already registered for “Timeline” property
body: <p>I am having a WPF application which is called by a client software. It works fine for the 1st time.When I closed the WPF application from the client software and again load the WPF app(without closing the client software in between)), it throws an exception as "Property Metadata is already registered for “Timeline” property" for the below code:</p>
  
  <pre><code>Timeline.DesiredFrameRateProperty.OverrideMetadata(typeof(Timeline),
                 new FrameworkPropertyMetadata { DefaultValue = 5 });
  </code></pre>
  
  <p>And then, I commented the above line of code from my app and again repeated the same scenario which I mentioned above, it throws an exception as "The caller thread cannot access this object because a different thread owns it" in Run().</p>
  
  <p>Below is the method which I am using Timeline property in my WPF application.</p>
  
  <pre><code>public void start()
  {
      Timeline.DesiredFrameRateProperty.OverrideMetadata(typeof(Timeline),
         new FrameworkPropertyMetadata { DefaultValue = 5 });
      //Property Metadata is already registered for the "Timeline" property.
  
      Run();
      // The caller thread cannot access this object because a different thread owns it.
  }
  </code></pre>