Question

In XAML I have:

<sdk:TreeView x:Name="navigationTreeView" Grid.Column="0" Grid.Row="1" SelectedItemChanged="TreeView_SelectedItemChanged">
    <sdk:TreeView.ItemContainerStyle>
        <Style TargetType="sdk:TreeViewItem">
            <Setter Property="IsExpanded" Value="True"/>
        </Style>
    </sdk:TreeView.ItemContainerStyle>

    <sdk:TreeView.ItemTemplate>
        <sdk:HierarchicalDataTemplate ItemsSource="{Binding Path=Nodes}">
            <StackPanel Orientation="Horizontal">
                <!--<Image Source="{Binding Path=ImageUri}" />-->
                <TextBlock Text="{Binding Path=Title}" ToolTipService.ToolTip="{Binding Path=Title}"/>                        
            </StackPanel>
        </sdk:HierarchicalDataTemplate>
    </sdk:TreeView.ItemTemplate>
</sdk:TreeView>

In code behind:

this.navigationTreeView.ItemsSource = nodes;
navigationTreeView.ExpandAll(); 

There are 1000 items as children of one node. If I’m not expanding elements everything is fine. But when I expand that node it’s pretty slow (10 sec maybe). What could I do to speed it up?

Silverlight 4, 2010 april toolkit.

Answer 1

Unlike WPF, Silverlight (until Silverlight 4, not sure about 5) does NOT support UI virtualization for hierarchical data, and this is why when you expand the node, the 1000 items which are inside the HierarchicalDataTemplate are not virtualized and take more than 10 seconds to load.

I believe Telerik’s RadTreeView has its built-in UI virtualization, but the control is not free.

The best solution I have found so far is from this site. Please note it is still a ListBox solution, however, because it doesn’t use HierarchicalDataTemplate, it is fully virtualized and looks exactly like a TreeView. Also by looking at the source code, it is quite easy to implement.

I know it is not the perfect answer for this question but at least give you some alternatives. 🙂