RadGridView expand/collapse notification with virtualiing panel

[Alan]

When virtualizing is turned on, a group is collapsed when its out of visible area and expands if it needs to when it returned to the visible area.  I need to display a count of all expanded groups for the user.  How can I get the "actual" expand count from the RadGridView?  Since the RadGridView is auto-expanded when they come back, it obviously knows whatn needs to be expanded.

[Yoan]

Hello Alan,

In order to achieve your goal, you can subscribe to the GroupRowIsExpandedChanged end execute the following logic:

public MainWindow()
      {
          InitializeComponent();
          this.clubsGrid.GroupRowIsExpandedChanged += new EventHandler<Telerik.Windows.Controls.GridView.GroupRowEventArgs>(clubsGrid_GroupRowIsExpandedChanged);
      }

      List<IGroup> expandedGroups = new List<IGroup>();

      void clubsGrid_GroupRowIsExpandedChanged(object sender, Telerik.Windows.Controls.GridView.GroupRowEventArgs e)
      {

          if (e.Row.IsExpanded)
          {
              this.expandedGroups.Add(e.Row.Group);
          }
          else
          {
              this.expandedGroups.Remove(e.Row.Group);
          }

      }

Regards,
Yoan
Telerik

[Alan]

You just decribed what I was doing that didn't work.  The issue is that when an expanded row moves out of the viewable area, the RadGridView collapses the group *for me*.  And when I say collapses then view, I mean it calls myGrid_GroupRowIsExpandedChanged with the IsExpanded = false.  So, in your example, the item would be removed from the List<IGroup> the moment it went out of view.  And that's the problem I have right now.  its not in the viewable area, but it should still be expanded.

[Dimitrina]

Hello,

Due to the UI Virtualization only the rows to be displayed in View of the GridView will be realized. When you scroll, the not-visible rows will be loaded and unloaded. This is explained in this help article.

That is why the myGrid_GroupRowIsExpandedChanged event is fired multiple times as you describe. Unfortunately there is not a public property holding the list of all the groups being expanded.

Regards,
Didie
Telerik