Can't get TreeViewItems to expand!!

Question

IF I did this:

<TreeView>
   <TreeViewItem>
       <TreeViewItem>
      <TreeViewItem>
   </TreeViewItem>
<TreeView>

Life would be good.  I can loo at the TreeView's Items collection, which is a collection of TreeViewITems....each of those have TreeViewItems as well.  All I have to do is find the TreeViewItem I want (navigating from the parent TreeviewItem so that the entire path is expanded) and say IsExpanded=true.

BUT...it doesn't work that way for me.

Instead of explicitly adding the items in a source xaml document, I am letting the treeview populate recursively using a Hierarchical data template that is bound to a class called "Folder."  This class has a property called "Subfolders" which contains an Observable collection of more folder instances.

Therefore, my XAML pretty much looks like:

...some XAML...

<HierarchicalDataTemplate DataType="{x:Type c:Folder}" ItemsSource="{Binding Subfolders}" >
     <TextBlock Text="{Binding Name}" />
</HierarchicalDataTemplate>

...some XAML...

<TreeView Name="FolderExplorer" SelectedValuePath="UncPath" />

...more XAML...

When I check The Treeview, it DOES have an Items Collection, but it returns a collection of Folder instances, not TreeViewItems.  I can not expand the TreeViewItems because I can't get a reference to the control.

Ultimately, I'd like to be able to pull up a list of folders and, if there is a known selected folder for a UNC path, have that folder expanded.  I'm not sure how this should work.

I tried adding a property to the Folder class named "IsInInitialUncPath" so taht the HierarchicalDataTemplate could be expanded when it binds.  However, there is no IsExpanded or IsSelected property available in the HierarchicalDataTemplate that I can bind to.

Any Ideas?

Answer 1

I have a sample on my blog which demonstrates how to do it:

The Tricks with TreeViewItem Expansion

BTW: Someone complains the download link is broken, I've tested it, and it works perfectly in my region, if you have the same problem downloading the sample, please let me know, I will try to fix it.

Sheva

Answer 2

oh wow.....

well.....it worked :-)

It's a lot of code.  But now that I look at it, it really does make sense.

 

Answer 3

This is the best way I found:

http://shevaspace.spaces.live.com/blog/cns!FD9A0F1F8DD06954!581.entry

Code Snippet

using System;
using System.Windows.Controls;
using System.Windows.Controls.Primitives;

namespace Sheva.Windows.Controls
{
    public static class TreeViewHelper
    {
        public static void ExpanAll(TreeView treeView)
        {
            ExpandSubContainers(treeView);
        }

        private static void ExpandSubContainers(ItemsControl parentContainer)
        {
            foreach (Object item in parentContainer.Items)
            {
                TreeViewItem currentContainer = parentContainer.ItemContainerGenerator.ContainerFromItem(item) as TreeViewItem;
                if (currentContainer != null && currentContainer.Items.Count > 0)
                {
                    currentContainer.IsExpanded = true;
                    if (currentContainer.ItemContainerGenerator.Status != GeneratorStatus.ContainersGenerated)
                    {
                        currentContainer.ItemContainerGenerator.StatusChanged += delegate
                        {
                            ExpandSubContainers(currentContainer);
                        };
                    }
                    else
                    {
                        ExpandSubContainers(currentContainer);
                    }
                }
            }
        }
    }
}

Thanks Sheva¡¡¡¡