title: Custom expand/collapse symbols in Silverlight TreeView using HierarchicalDataTemplate
body: <p>I have a TreeView control where nodes are dynamically built using a HierarchicalDataTemplate. In other words, no TreeViewItems are explicitly defined in the XAML. TreeViewItems are instead created automatically when the data are bound at runtime (I can see them in Silverlight Spy).</p>
  
  <p>Is it possible to customize the expand/collapse symbols (paths) within the TreeView in this case? Clients hate the default triangles as being hard to see and use. I've found references to doing this kind of thing, but only where the TreeViewItems are set up explicitly, so that a Style can be set in the XAML of the page. Another way of asking this I guess is whether it's possible to define and apply a style for the TreeViewItem when they are not in the XAML markup (or added in code as TreeViewItem).</p>