CODEWITHSUNDEEP
silverlighttreeview
Sven Sönnichsen
Sven Sönnichsen

Reputation: 945

How to select an item in the Silverlight Treeview?

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           }

Upvotes: 2

Views: 6924

Answers (3)

Toby
Toby

Reputation: 31

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!

Upvotes: 1

Sven S&#246;nnichsen
Sven S&#246;nnichsen

Reputation: 945

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;
  }
}

Upvotes: 3

Jon Galloway
Jon Galloway

Reputation: 53155

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:

Upvotes: 2

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