title: WPF trigger can't change a property in mvvm
body: <p>I wanted to make it happened to change property in ViewModel using <code>Trigger</code> tag in xaml.</p>
  
  <p>The code I made was like this.</p>
  
  <pre><code>        &lt;Grid x:Name="LogoGrid"&gt;
              &lt;Grid.Style&gt;
                  &lt;Style TargetType="Grid"&gt;
                      &lt;Setter Property="Height" Value="{Binding LogoHeight, Mode=TwoWay}"/&gt;
  
                      &lt;Style.Triggers&gt;
                          &lt;DataTrigger Binding="{Binding RelativeSource={RelativeSource AncestorType=Grid}, Path=ActualHeight, Converter={StaticResource ImageHeight}}" Value="False"&gt;
                              &lt;Setter Property="Height" Value="150"/&gt;
                          &lt;/DataTrigger&gt;
                      &lt;/Style.Triggers&gt;
                  &lt;/Style&gt;
              &lt;/Grid.Style&gt;
              &lt;Image Source="/Resources/Logo/Logo.png" Style="{StaticResource GameWindowLogoStyle}"/&gt;
          &lt;/Grid&gt;
  </code></pre>
  
  <p>I bound data to <strong><em>LogoHeight</em></strong> property in ViewModel and I wanted to set this property to 150 when parents grid is big enough to show Logo Image.</p>
  
  <p>It works fine in the UI. but it didn't change <strong><em>LogoHeight</em></strong> property.
  It is the same things keep happening when I use animation with <code>Storyboard</code> tag.</p>
  
  <p>Is it normal things that propery can't be changed by <code>Trigger</code> tag or animation in the <code>Storyboard</code> tag.</p>
  
  <p>Please tell me the way if there is a way to change property in <code>Trigger</code> tag or <code>Storyboard</code> tag.</p>
  
  <p>Thank you.</p>