title: Set hidden AttachedProperty through Style
body: <p>I've got a problem using <em>System.Windows.Interactivity.Interaction</em> attached behavior class (from Expression Blend SDK 4). I'd like to define a pair of triggers for <em>System.Windows.Window</em> class in XAML Style element. But as the <em>TriggersProperty</em> field of <em>System.Windows.Interactivity.Interaction</em> class is private and there is no <em>SetTriggers</em> method in this class, I've got an error <em>'Set property System.Windows.Setter.Property threw an exception. -> Value cannot be null. Parameter name: property'</em> when running the following code.</p>
  
  <p>I really want to use the triggers and actions in styles, because I'd like to use them for my window-descendant control. Of course I can use my custom behavior or directly code my window-descendant class with triggers-analogue logic, but I'd like to use already existent triggers and actions of the expression library and my own, not declining them, simply because the <em>TriggersProperty</em> of Interaction class is hidden and I can't set it through style.</p>
  
  <p>Is any workaround for the problem? With Reflection or someway other?</p>
  
  <p>PS. I already tried to declare custom static class with <em>TriggersProperty</em> attached dependency property, registered with the help of <em>AddOwner</em> method, but no help - at the end it still tries to access the same <em>TriggersProperty</em> in the same <em>System.Windows.Interactivity.Interaction</em> class.</p>
  
  <pre><code>&lt;Window
      x:Class="WpfApplication1.MainWindow"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:windowsInteractivity="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"&gt;
      &lt;Window.Style&gt;
          &lt;Style TargetType="Window"&gt;
              &lt;Setter Property="Title" Value="WindowStyleTest"/&gt;
              &lt;Setter Property="windowsInteractivity:Interaction.Triggers"&gt;
                  &lt;Setter.Value&gt;
                      &lt;windowsInteractivity:EventTrigger EventName="MouseDown"/&gt;
                  &lt;/Setter.Value&gt;
              &lt;/Setter&gt;
          &lt;/Style&gt;
      &lt;/Window.Style&gt;
  &lt;/Window&gt;
  </code></pre>