How to select an item in the Silverlight Treeview?

Question

I am having problems to select the first TreeViewItem in a TreeView in Silverlight. The following code just gives a null value in the method SelectFistItemInCatTreeView. Why? Any ideas?

<controls:TreeView  x:Name="treeCategories" Grid.Column="1" Grid.Row="2" SelectedItemChanged="treeCategories_SelectedItemChanged">
  <controls:TreeView.ItemTemplate>
    <common:HierarchicalDataTemplate  ItemsSource="{Binding SubCats}">
      <StackPanel >
        <TextBlock Text="{Binding Name}"></TextBlock>
      </StackPanel>
    </common:HierarchicalDataTemplate>
  </controls:TreeView.ItemTemplate>
</controls:TreeView> 



1            public MainPage()
2            {
3                InitializeComponent();
4    
5                DBService.DocTrackingServeceClient webService = new DockTracking.DBService.DocTrackingServeceClient();
6                webService.GetDocCategoriesCompleted += new EventHandler(webService_GetDocCategoriesCompleted);
7                webService.GetDocCategoriesAsync();
8                treeCategories.Loaded += new RoutedEventHandler(treeCategories_Loaded);
9            }
10   
11           void webService_GetDocCategoriesCompleted(object sender, DockTracking.DBService.GetDocCategoriesCompletedEventArgs e)
12           {
13   
14               List cats = new List();
15               cats = GetCats(e.Result.ToList(), null);
16               treeCategories.ItemsSource = cats;
17           }
18   
19           void treeCategories_Loaded(object sender, RoutedEventArgs e)
20           {
21               SelectFistItemInCatTreeView();
22           }
23   
24           private void SelectFistItemInCatTreeView()
25           {
26               TreeViewItem item = treeCategories.ItemContainerGenerator.ContainerFromItem(treeCategories.Items[0]) as TreeViewItem;
27               if (item != null)
28               {
29                   item.IsSelected = true;
30               }
31           }

score 3 · Accepted Answer · answered Sep 09 '09 at 07:34

Calling UpdateLayout() prior to get the TreeViewItem does the trick:

private void SelectFistItemInCatTreeView()
{

  treeCategories.UpdateLayout();

  TreeViewItem item = treeCategories.ItemContainerGenerator.ContainerFromItem(treeCategories.Items[0]) as TreeViewItem;
  if (item != null)
  {
    item.IsSelected = true;
  }
}

score 2 · Answer 2 · edited May 23 '17 at 12:07

2

It looks like the ContainerFromItem method is supposed to be passed the actual item you're binding to, rather than just an tv.Items[0].

I'd look at the following:

Post by Justin Josef-Angel about using the ContainerFromItem method
Previous SO question about selecting a TreeViewItem in code

edited May 23 '17 at 12:07

Community

1
1

answered Sep 08 '09 at 17:09

Jon Galloway

52,327
25
125
193

score 1 · Answer 3 · edited Aug 16 '12 at 21:20

1

If you have Hierarchical data, this will only work when selecting items at the top level. To select subitems underneath the top level, you have to expand and traverse the tree til the TreeViewItem for the desired item has been created.

See this page for TreeViewExtended

His TreeViewExtended class has a method called SetSelectedItem that actually works!

edited Aug 16 '12 at 21:20

SeanC

15,695
5
45
66

answered Apr 26 '10 at 18:36

Toby

31
1

I've tried the SetSelectedItem method, but it did not work for me. Anyway the aricle about the treeview is great, and helped me in other situations. – Sven Sönnichsen May 05 '10 at 13:06
Link no longer working. Thank you microsoft for messing up with all silverlight resources links. – Nikos Tsokos Nov 13 '12 at 14:33

How to select an item in the Silverlight Treeview?

3 Answers3