Large performance hit on e.Item.Expanded = true

[Eric]

In the ItemCommand event on my RadGrid I have the following section:
if (e.CommandName == RadGrid.ExpandCollapseCommandName || e.CommandName.Equals("RowClick",StringComparison.InvariantCultureIgnoreCase)) {
                e.Item.Expanded = true;
                e.Item.Selected = true;
   }

The e.Item.Expanded being set to true is taking 10-14 seconds to resolve, what could be happening that would cause such a large performance hit? 

[Pavlina]

Hi Eric,

If you have hierarchical grid, use on demand loading (HierarchyLoadMode.ServerOnDemand) of detail tables with DetailTableDataBind child tables content generation. You can combine these settings with:
single expand for grid items at the same level:
http://www.telerik.com/help/aspnet-ajax/grid-single-expand-in-hierarchical-grid.html

More useful tips for optimizing grid performance are available here:
http://www.telerik.com/help/aspnet-ajax/grid-viewstate-reduction-techniques.html

Regards,
Pavlina
Telerik