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POWPF: Cannot Get Custom Attached Property to work as a Trigger Property
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  1. POWPF: Cannot Get Custom Attached Property to work as a Trigger Property
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    copied!<p>So I have a class that looks like this:</p> <pre><code>internal class MyClass { public static readonly DependencyProperty IsSomethingProperty = DependencyProperty.RegisterAttached( "IsSomething", // property name typeof(bool), // property type typeof(MyClass), // owner type new FrameworkPropertyMetadata(false) ); public static void SetIsSomething(DependencyObject obj, bool value) { obj.SetValue(IsSomethingProperty, value); } [AttachedPropertyBrowsableForType(typeof(TreeViewItem))] public static bool GetIsSomething(DependencyObject obj) { return (bool)obj.GetValue(IsSomethingProperty); } } </code></pre> <p>I would like to be able to use this attached property as a trigger property in a control template, like so:</p> <pre><code>&lt;ControlTemplate TargetType="TreeViewItem"&gt; &lt;!-- stuff here omitted for brevity --&gt; &lt;Trigger Property="my:MyClass.IsSomething" Value="True"&gt; &lt;!-- setters for when IsSomething is True --&gt; &lt;/Trigger&gt; &lt;/ControlTemplate&gt; </code></pre> <p>(the above control template assumes the proper <code>xmlns:my="clr-namespace:MyAssembly"</code> where MyAssembly contains MyClass is in the enclosing XAML file)</p> <p>Here's my trouble: when I do this, it compiles fine. However, when I try to see this control template in action in the designer, it complains <code>Cannot find the 'IsSomething' template property on type 'System.Windows.Controls.TreeViewItem'.</code> and the designer won't load.</p> <p>I've tried the <code>RegisterAttached</code> override with <code>MyClass</code> as well as <code>TreeViewItem</code> as the owner type, neither fixes this. I've also tried it with and without the <code>AttachedPropertyBrowsableForType</code> attribute on <code>GetIsSomething</code>. Does anyone see what the problem is?</p>
 

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