title: How can I toggle a TextBlock's visibility in a DataTrigger?
body: <p>This code <strong>works</strong> (when ControlType="dropDown" then the background <strong>yellow</strong>):</p>
  
  <pre><code>&lt;Window x:Class="TestCollapsed.Views.MainView"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:c="clr-namespace:TestCollapsed.Commands"
      Title="Main Window" Height="400" Width="800"&gt;
      &lt;Window.Resources&gt;
          &lt;Style x:Key="DropDownStyle" TargetType="TextBlock"&gt;
              &lt;Style.Triggers&gt;
                  &lt;DataTrigger Binding="{Binding ControlType}" Value="dropDown"&gt;
                      &lt;Setter Property="Background" Value="Yellow"/&gt;
                  &lt;/DataTrigger&gt;
              &lt;/Style.Triggers&gt;
          &lt;/Style&gt;
      &lt;/Window.Resources&gt;
  
      &lt;StackPanel&gt;
          &lt;TextBlock Visibility="Visible" 
                     Text="This is going to be the dropdown control."
                     Style="{StaticResource DropDownStyle}"/&gt;
      &lt;/StackPanel&gt;
  &lt;/Window&gt;
  </code></pre>
  
  <p>But this code does <strong>not</strong> work (when ControlType="dropDown" then the TextBlock is still <strong>invisible</strong>):</p>
  
  <pre><code>&lt;Window x:Class="TestCollapsed.Views.MainView"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:c="clr-namespace:TestCollapsed.Commands"
      Title="Main Window" Height="400" Width="800"&gt;
      &lt;Window.Resources&gt;
          &lt;Style x:Key="DropDownStyle" TargetType="TextBlock"&gt;
              &lt;Style.Triggers&gt;
                  &lt;DataTrigger Binding="{Binding ControlType}" Value="dropDown"&gt;
                      &lt;Setter Property="Visibility" Value="Visible"/&gt;
                  &lt;/DataTrigger&gt;
              &lt;/Style.Triggers&gt;
          &lt;/Style&gt;
      &lt;/Window.Resources&gt;
  
      &lt;StackPanel&gt;
          &lt;TextBlock Visibility="Collapsed" 
                     Text="This is going to be the dropdown control."
                     Style="{StaticResource DropDownStyle}"/&gt;
      &lt;/StackPanel&gt;
  &lt;/Window&gt;
  </code></pre>
  
  <p><strong>Why can't I set visibility in a style as I can background?</strong></p>