title: navigationservice has no constructors defined
body: <p>I am using Visual Studio Express 2012 for Windows Phone and building an app targeting Windows Phone 7.1.</p>
  
  <p>I am trying to use NavigationService to navigate to a different page but I keep running into problems.</p>
  
  <p>Here is my code:</p>
  
  <pre><code>private void GotoDetails(object _url)
      {
          var url = string.Format("/DetailsPage.xaml?url={0}", _url.ToString());
          NavigationService nav = new NavigationService();
          nav.Navigate(new Uri(url, UriKind.Relative));
      }
  </code></pre>
  
  <p>when I try to build this I get a "The type 'System.Windows.Navigation.NavigationService' has no constructors defined" on the NavigationService nav =.... line.</p>
  
  <p>If I try to do just NavigationService.Navigate(new Uri(url, UriKind.Relative)); then I get a "An object reference is required for the non-static field, method, or property 'System.Windows.Navigation.NavigationService.Navigate(System.Uri)'" error. </p>
  
  <p>update: I am trying to use MVVM (for the first time). This code resides in my view model. I am not using any frameworks. Just trying to learn it from scratch.</p>
  
  <p>I have searched the intertubes but cannot seem to find a solution.</p>
  
  <p>Any help is much appreciated.</p>
  
  <p>Kamal</p>