title: Play Url video in WPF MediaElement
body: <p>I get url form vimeo and i want to play on MediaElement but I have problem like this.</p>
  
  <pre><code>var FullVimeoUrl = "https://pdlvimeocdn-a.akamaihd.net/36507/517/262124023.mp4?token2=1428493810_25ff23eaeb9489b76649aaaf3e7fa438&amp;aksessionid=028dcbd66a5e2a5a"
  
  mediaElement.Source = new Uri(FullVimeoUrl.ToString(), UriKind.RelativeOrAbsolute);
  mediaElement.Play();
  </code></pre>
  
  <p>Problem: </p>
  
  <blockquote>
    <p>An exception of type 'System.NullReferenceException' occurred in
    PresentationCore.dll but was not handled in user code</p>
    
    <p>Additional information: Object reference not set to an instance of an
    object. Please help and solution for me thank.</p>
  </blockquote>