How can I change my treeview's visual to automatically display a SelectedItem?

Question

Possible Duplicate:
WPF TreeView - How to scroll so expanded branch is visible

I'm developing an application that utilizes the standard TreeView functionality in WPF. I've created a search function within the TreeView that will parse through the tree and locate a matching title (e.g. "Create" will work for finding a TreeViewItem titled "Create a Project:". If I press the "enter" key while the search textbox still has focus, it'll parse through the tree for the next possible TreeViewItem. The search functionality is inspired by the code found here at Josh Smith's TreeView Article, but modified slightly to work within the resources of my application and its nodes (the trees generated are dynamic, depending on the files imported in the application, and I obviously have my own Object classes).

When I tried to look up this issue, I found a million and one search hits for how to set the SelectedItem for the TreeView (which I'm not having an issue with), but I couldn't find anything specifically for my problem which is this: Every time I do a search, the tree will find the SelectedItem (if it exists), and call IsExpanded = true to all the elements recursively up to the root of the tree. But sometimes the element discovered is outside of the visual frame of the TreeView (I have scrollbars set to auto, so when the tree grows too large horizontally or vertically, scroll bars are enabled). The SelectedItem changes appropriately, but I have to scroll down the TreeView in order to find where my match was made. What I'm hoping to do is fire an event that will detect when the SelectedItem is changed, and then force the Visual of the TreeView to show the selected item at some point within its visible frame (so it's never out of visibility if found), but I'm not sure how exactly to do this (my experience with WPF is limited to the last month or so I've spent developing this application, so I'm still new to the language and picking things up as I go along).

Are there any solutions for this? I can provide code if desired, but I'm just looking for somebody to point me in the right direction on how to change the visible region of my TreeView item.

TL;DR - please try to phrase your questions more concisely. Basically, you are asking: "How can I scroll the selected item of a WPF TreeView into view when using the MVVM pattern?". — Daniel Hilgarth, Aug 23 '11 at 17:52
Apologies, this was actually my first post on S.O. so I opted to be more detailed rather than less detailed. Appreciate the feedback, nonetheless. — Matt Starn, Aug 23 '11 at 20:56
I know that this was your first post, that's why I wrote the little pointer. Your question was simple, but I think most didn't bother reading this big blob of text. "Be as short as possible and as long as necessary" — Daniel Hilgarth, Aug 23 '11 at 21:07

score 4 · Accepted Answer · edited May 23 '17 at 12:07

4

You need to call BringIntoView on the selected TreeViewItem. To not pollute your ViewModel with this code, you could create an Attached Property that calls this method when it is set to true and bind it to the IsSelected property.

Another way is to use a trigger on the IsSelected property to call this method as shown here.

edited May 23 '17 at 12:07

Community

1
1

answered Aug 23 '11 at 17:47

Daniel Hilgarth

171,043
40
335
443

Went with the "IsSelected" property trigger because I already had one set up to "bold" the text of the selected item when found (so all I had to do was add another setter). Worked like a charm, once I created the DependencyProperty. Thanks for the help! – Matt Starn Aug 23 '11 at 18:31

score 3 · Answer 2 · answered Feb 29 '12 at 06:14

You can use a simple EventSetter in TreeViewItem style to invoke an event handler when the item is selected. Then call BringIntoView for the item.

<TreeView >
 <TreeView.ItemContainerStyle>
   <Style TargetType="{x:Type TreeViewItem}">
     <EventSetter Event="Selected" Handler="TreeViewSelectedItemChanged" />
   </Style>
 </TreeView.ItemContainerStyle>

</TreeView>

private void TreeViewSelectedItemChanged(object sender, RoutedEventArgs e)
{
    TreeViewItem item = sender as TreeViewItem;
    if (item != null)
    {
        item.BringIntoView();
        e.Handled = true;  
    }
}

How can I change my treeview's visual to automatically display a SelectedItem?

2 Answers2