OnNodeSelect client-side event of WebTreeView is used to collect the last position of the vertical scrollbar by obtaining the scrollTop property then store the value in HiddenField control. The OnNodeSelect client-side event specifies the client side (JavaScript) function name that will be invoked when node is selected. Parameters: (controlsId, node).

function WebTreeView1_OnNodeSelect(controlId, node)
{
    // collecting the last position
    // of the vertical scrollbar
    // by obtaining the scrollTop property

    var treeView = ISGetObject(controlId);
    var frameElement = treeView.GetFrameElement();

    // obtain the scrollTop property 
    // of the vertical scrollbar
    var verticalPosition = frameElement.children[0].scrollTop;

    // store the value scrollTop position in HiddenField control
    form1.ValueHiddenField.value = verticalPosition;

    return true;
}

Next, invoke the ApplyLatestScroll() JavaScript function from OnNodeSelectChanged event.

protected void WebTreeView1_NodeSelectChanged(object sender, ISNet.WebUI.WebTreeView.WebTreeViewNodeEventArgs e)
{
    // This event fires after the selected treeview nodes are changed.

    // invoke ApplyLatestScroll() function to set back the scroll position.
    Page.ClientScript.RegisterStartupScript(this.GetType(), "ApplyLatestScroll", "ApplyLatestScroll();", true);
}

The ApplyLatestScroll() JavaScript function is:

function ApplyLatestScroll()
{
    // set back the previous scrollTop property or
    // vertical scroll position

    var treeView = ISGetObject("WebTreeView1");
    var frameElement = treeView.GetFrameElement();
            
    // manually configure the vertical scroll position
    frameElement.children[0].scrollTop = form1.ValueHiddenField.value;

    return true;
}

I enclosed my simple sample for your reference. Please let me know whether this helps or not.

Hi Shailendra,

you could set the button function similiar to TreeView NodeSelect, for example:

function ApplyLatestScroll() {    var treeView = ISGetObject("WebTreeView1");    var frameElement = treeView.GetFrameElement();    frameElement.children[0].scrollTop = form1.ValueHiddenField.value;

    return true;
}

After that, invoke the ApplyLatestScroll() function from OnInitializeNode event.

protected void WebTreeView1_InitializeNode(object sender, ISNet.WebUI.WebTreeView.WebTreeViewNodeEventArgs e) {
     Page.ClientScript.RegisterStartupScript(this.GetType(), "ApplyLatestScroll", "ApplyLatestScroll();", true);
 }