Load On Demand Expand on Server-side NodeClick

Case:

A Load On Demand TreeView for which:

• The ExpandMode for Load On Demand Nodes is either ServerSideCallBack or WebService.

• The NodeClick server-side event is handled.

• A Node is expanded when clicked (in either the OnClientNodeClicking or OnClientNodeClicked event handlers).

Problem:

Due to timing issues in case ExpandMode for the clicked Node is:

• ServerSideCallBack - the Node does not expand after the postback although its child Nodes are loaded.

• WebService - the Web Method fails.

Resolution:

Ensure that the NodeClick event fires after the Node finishes loading its Nodes:

1. Expand the Node in the OnClientNodeClicking event handler. If the Node's ExpandMode is ServerSideCallBack or WebService and the Node does not have children, cancel the event. Below is an example:

   function onClientNodeClicking(sender, eventArgs){
   
   var node = eventArgs.get_node();
   
   if ((node.get_expandMode() > 1) &&
    (node.get_nodes().get_count() == 0))
   {
    eventArgs.set_cancel(true);
   }
   
   node.expand();
   }
   

2. Handle the OnClientNodePopulated event and select the expanded Node in the event handler, like this:

   function onClientNodePopulated(sender, eventArgs){ 
   
   eventArgs.get_node().select();
   }