It was on one of the other forums that this reqiurement was put. It was required to collapse all treeview nodes on the client with javascript.

So, i wrote some script to accomplish the task and realizing that the script to Expand all nodes will not be  very different, i did a minor modification to get it working for the expand all case. Now with this script we can save a server trip for just expanding or collapsing all nodes. I have tested the script in IE7 & FF2.0 and it works fine in both. Below i give the script:

1)Expand all nodes

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function expandAll(treeViewId)
    {
         var treeView = document.getElementById(treeViewId);
         var treeLinks = treeView.getElementsByTagName("a");
         var j = true;
         for(i=0;i<treeLinks.length;i++)
         {
              if(treeLinks[i].firstChild.tagName == "IMG")
              {
                var node = treeLinks[i];
                var level = parseInt(treeLinks[i].id.substr(treeLinks[i].id.length - 1),10);
                var childContainer = document.getElementById(treeLinks[i].id + "Nodes");
               
               if(j)
                {
                    if(childContainer.style.display == "none")
                    TreeView_ToggleNode(eval(treeViewId +"_Data"),level,node,'r',childContainer);
                    j = false;
                }
                else
                {
                    if(childContainer.style.display == "none")
                    TreeView_ToggleNode(eval(treeViewId +"_Data"),level,node,'l',childContainer);
                }
              }
          }
   }              

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2)Collapse all nodes:

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function collapseAll(treeViewId)
    {
         var treeView = document.getElementById(treeViewId);
         var treeLinks = treeView.getElementsByTagName("a");
         var j = true;
         for(i=0;i<treeLinks.length;i++)
         {
              if(treeLinks[i].firstChild.tagName == "IMG")
              {
                var node = treeLinks[i];
                var level = parseInt(treeLinks[i].id.substr(treeLinks[i].id.length - 1),10);
                var childContainer = document.getElementById(treeLinks[i].id + "Nodes");
               
               if(j)
                {
                    if(childContainer.style.display == "block")
                    TreeView_ToggleNode(eval(treeViewId +"_Data"),level,node,'r',childContainer);
                    j = false;
                }
                else
                {
                    if(childContainer.style.display == "block")
                    TreeView_ToggleNode(eval(treeViewId +"_Data"),level,node,'l',childContainer);
                }
              }
          }
   }     

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The functions require the treeview id to be passed. Hope this works fine.

cheers!!