title: Image tap event with Xamarin.Forms and Prism
body: <p>I'm developing a cross platform application with Xamarin. The framework used for MVVM is Prism.
  In my user interface there is an image, I need that it raise an action when it's tapped.
  I tried with TapGestureRecognizer but it doesn't work. Where is the error? There is another way to do that?</p>
  
  <p><strong>XAML:</strong></p>
  
  <pre><code>            ...&lt;Frame Grid.Row="0" Grid.Column="0" OutlineColor="Black" Padding="5"&gt;
              &lt;Image x:Name="imgSynch" Source="synch.png" &gt;                    
                  &lt;Image.GestureRecognizers&gt;
                      &lt;TapGestureRecognizer Command="Binding TapCommand" /&gt;
                  &lt;/Image.GestureRecognizers&gt;
              &lt;/Image&gt;
          &lt;/Frame&gt;...
  </code></pre>
  
  <p><strong>ViewModel:</strong></p>
  
  <pre><code>... ICommand tapCommand;
  
      public ICommand TapCommand
      {
          get { return tapCommand; }
      }
      public MainPageViewModel()
      {                            
          var tapImageSynch = new TapGestureRecognizer();
          tapCommand = new Command(Synch);
      void Synch()
      {
          _pageDialogService.DisplayAlertAsync("Title", "It works!", "OK");
      } ...
  </code></pre>
  
  <p>Thanks!</p>