Get ASP.NET TreeView – get selected node id on the client side

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TreeViewClientID_Data.selectedNodeID.value 

where TreeViewClientID_Data  is the name of the TreeView javascript object that has “selectedNodeID” property.

We can easily load this object and get selected node id like this:

   1:          Sys.WebForms.PageRequestManager.getInstance().add_pageLoaded(EndLoadedHandler);

   2:   

   3:          function EndLoadedHandler(sender, args)

   4:          {

   5:                   //* make sure that object is fully loaded

   6:                    var data = eval('<%=tvwScrollTo.ClientID %>_Data');

   7:                    if(!data)

   8:                         var selectedNodeID = data.selectedNodeID.value;

   9:           }

we have to make sure that TreeViewClientID_Data  is loaded.

or

document.getElementById('TreeViewClientID_SelectedNode').value 

where TreeViewClientID_SelectedNode is the id of the hidden field where selected node id is stored

Explained:

TreeViewClientID_Data has a lot of useful information. You can find this object in the source of the page:

We can clearly see that selected node id is stored in the hidden field with the name 'TreeViewClientID_SelectedNode'

So, lets grab it:

document.getElementById('TreeViewClientID_SelectedNode').value 

or dynamically

document.getElementById('<%=tvwScrollTo.ClientID %>_SelectedNode').value

Happy programming!