title: How to use Resource Dictionary by its Key?
body: <p>I am trying to use my <code>Resource Dictionary</code> but it does not recognize the styles  have created.</p>
  
  <pre><code>&lt;Window.Resources&gt;
      &lt;RoutedUICommand x:Key="Add" Text="Add" /&gt;
      &lt;RoutedUICommand x:Key="Cancel" Text="Cancel" /&gt;
      &lt;RoutedUICommand x:Key="Exit" Text="Exit" /&gt;
      &lt;ResourceDictionary x:Key="LightTheme" Source="/Themes/Light.xaml"/&gt;
  &lt;/Window.Resources&gt;
  </code></pre>
  
  <p>When I delete <code>x:Key</code> from ResourceDictionary tag, it shows a message saying "<strong>Each dictionary must have an associated key</strong>"</p>
  
  <p>But when I try to use one of my styles, it does not work.</p>
  
  <pre><code>&lt;Button x:Name="AddNew" Style="{StaticResource RoundCorner}"&gt;
  </code></pre>