title: Silverlight 4 default value for dependency property using the default value of another dependency property
body: <p>I am trying to use the default value of the textblock's property for a control by using:</p>
  
  <pre><code> public static readonly DependencyProperty FontFamilyProperty = DependencyProperty.Register(
                               "FontFamily", typeof(FontFamily), typeof(IMTextBlock), new PropertyMetadata(TextBlock.TextProperty.GetMetadata(typeof(FontFamily)).DefaultValue));
  </code></pre>
  
  <p>I am getting this error:</p>
  
  <pre><code>  The invocation of the constructor on type 'Common.Infrastructure.Controls.IMTextBlock' that matches the specified binding constraints threw an exception.
  </code></pre>
  
  <p>What is the right way to do this?</p>
  
  <pre><code> TextBlock.TextProperty.GetMetadata(typeof(FontFamily)).DefaultValue
  </code></pre>
  
  <p>is not getting me the correct default value, or maybe I am not using it correctly. Any help is greatly appreciated. Thanks in advanced.</p>