TreeView BringIntoView with MVVM

Question

I want the user to be able to search for Items in a TreeView. After entering a searchtext the TreeViewItem should be scrolled into view.

Right now I am using the MVVM Pattern for the TreeView, for the TreeViewItems and the MainView.

What do I have to do to get the functionality of BringIntoView utilizing MVVM? Is there some property I can bind? (in MFC there was something like FirstVisibileItem)

Have seen a "solution" with a behavior. Is it really necessary?

Answer 1

According to the mentioned Code Project article, here is the Code example that shows how to setup the Behavior and how to integrate the Behavior in XAML.

Setup the behavior:

/// <summary>
/// Exposes attached behaviors that can be
/// applied to TreeViewItem objects.
/// </summary>
public static class TreeViewItemBehavior
{
    #region IsBroughtIntoViewWhenSelected
    public static bool GetIsBroughtIntoViewWhenSelected(TreeViewItem treeViewItem)
    {
        return (bool)treeViewItem.GetValue(IsBroughtIntoViewWhenSelectedProperty);
    }

    public static void SetIsBroughtIntoViewWhenSelected(      TreeViewItem treeViewItem, bool value)
   {
       treeViewItem.SetValue(IsBroughtIntoViewWhenSelectedProperty, value);
   }

   public static readonly DependencyProperty IsBroughtIntoViewWhenSelectedProperty =
    DependencyProperty.RegisterAttached(
    "IsBroughtIntoViewWhenSelected",
    typeof(bool),
    typeof(TreeViewItemBehavior),
    new UIPropertyMetadata(false, OnIsBroughtIntoViewWhenSelectedChanged));

    static void OnIsBroughtIntoViewWhenSelectedChanged(DependencyObject depObj, DependencyPropertyChangedEventArgs e)
    {
        TreeViewItem item = depObj as TreeViewItem;
        if (item == null)
           return;

        if (e.NewValue is bool == false)
           return;

        if ((bool)e.NewValue)
           item.Selected += OnTreeViewItemSelected;
        else
           item.Selected -= OnTreeViewItemSelected;
    }

    static void OnTreeViewItemSelected(object sender, RoutedEventArgs e)
    {
       // Only react to the Selected event raised by the TreeViewItem
       // whose IsSelected property was modified. Ignore all ancestors
       // who are merely reporting that a descendant's Selected fired.
       if (!Object.ReferenceEquals(sender, e.OriginalSource))
         return;

       TreeViewItem item = e.OriginalSource as TreeViewItem;
       if (item != null)
          item.BringIntoView();
    }

    #endregion // IsBroughtIntoViewWhenSelected
}

Then integrate the TreeViewItemBehavior in XAML:

<TreeView.ItemContainerStyle>
  <Style TargetType="{x:Type TreeViewItem}">
    <Setter Property="local:TreeViewItemBehavior.IsBroughtIntoViewWhenSelected" Value="True"/>
  </Style>
</TreeView.ItemContainerStyle>

Have fun :-)

Answer 2

The problem can be solved with an Behavior.

This CodeProject article describes it very good and it works out of the box.