How to programmatically select an item in a WPF TreeView?

Question

How is it possible to programmatically select an item in a WPF TreeView? The ItemsControl model seems to prevent it.

Answer 1

I have created a method VisualTreeExt.GetDescendants that returns an enumerable collection of elements that match the specified type:

public static class VisualTreeExt
{
  public static IEnumerable GetDescendants(DependencyObject parent) where T : DependencyObject
  {
    var count = VisualTreeHelper.GetChildrenCount(parent);
    for (var i = 0; i < count; ++i)
    {
       // Obtain the child
       var child = VisualTreeHelper.GetChild(parent, i);
       if (child is T)
         yield return (T)child;

       // Return all the descendant children
       foreach (var subItem in GetDescendants(child))
         yield return subItem;
    }
  }
}

When you ask for VisualTreeHelperExt.GetDescendants(MyAmazingTreeView) you'll get all the TreeViewItem childs. You can select a particular value using the following piece of code:

var treeViewItem = VisualTreeExt.GetDescendants(MyTreeView).FirstOrDefault(tvi => tvi.DataContext == newValue);
if (treeViewItem != null)
  treeViewItem.IsSelected = true;

It's a bit of a dirty solution (and probably not the most efficient) and won't work if you're using a virtualized TreeView, because it depends on the existance of the actual visual elements. But it works for my situation...