title: WPF Dependency Properties: Why do I need to specify an Owner Type?
body: <p>This is how I register a <code>DependencyProperty</code>:</p>
  
  <pre><code>    public static readonly DependencyProperty UserProperty = 
          DependencyProperty.Register("User", typeof (User), 
               typeof (NewOnlineUserNotifier));                                                                                                                 
  
  
      public User User
      {
          get
          {
              return (User)GetValue(UserProperty);
          }
          set
          {
              SetValue(UserProperty, value);
          }
      }
  </code></pre>
  
  <p>The third parameter of the <code>DependencyProperty.Register</code> method requires you to specify the type of the Control where the Dependency Property resides in  (in this case, my User Control is called <code>NewOnlineUserNotifier</code>).</p>
  
  <p>My question is, <strong>why do you actually specify the type of the owner, and what happens if you specify a different type than the actual owner's ?</strong></p>