Hello,

I apologize for the late response.

Basically, we can’t use “Load on Demand” scenario or feature in (TreeView) node that already has children (child node).

I attached a page that contains ASP.Net TreeView to show how the “Load on Demand” feature of ASP.Net TreeView works.

In this page, I add “OnTreeNodePopulate” server side event to the TreeView control.

On the “Page_Load” server side event, I create the root node for the TreeView:

protected void Page_Load(object sender, EventArgs e){
    if (!IsPostBack)
    {
        TreeNode rootNode = new TreeNode();
        rootNode.Text = "Root";
        rootNode.Value = "Level0";
        rootNode.Expanded = true;
        rootNode.PopulateOnDemand = true;

        TreeView1.Nodes.Add(rootNode);
    }
}

Then in “OnTreeNodePopulate” server side event I try to add two nodes with different depth level.

protected void TreeView1_TreeNodePopulate(object sender, TreeNodeEventArgs e)
{
    TreeNode newNode = new TreeNode();
    newNode.Text = "Level One";
    newNode.Value = "Level1";
    newNode.PopulateOnDemand = false;

    TreeNode newNode2 = new TreeNode();
    newNode2.Text = "Level Two";
    newNode2.Value = "Level2";
    newNode2.PopulateOnDemand = true;

    newNode.ChildNodes.Add(newNode2);
    e.Node.ChildNodes.Add(newNode);
}

With this configuration the ASP.Net TreeView will work properly. However, if you try to modify the “PopulateOnDemand” property, in “newNode”, to “True”.
You will get the warning message while you are trying to expand the root node.

I attached the video regarding the result on my end as well.

As you can see, the Intersoft WebTreeView have the same default behavior with ASP.Net TreeView, that the “Load on Demand” scenario or feature can’t be applied in (TreeView) node that already has children (child node).

Due to that behavior, in this Load on Demand scenario, the WebTreeView will only load the parent node, not with its child node.

Hope this helps.

Regards,
Hans K.

Hi,

thanks for your time, you are right, in our scenario I can keep PopulateOnDemand = false for this nodes and I combine our two scenarios... But I can still do in ASP:TreeView this (basicaly ExpandToNode / ExpandToNodes functionality)

protected void TreeView1_TreeNodePopulate(object sender, TreeNodeEventArgs e)    {
        TreeNode n = new TreeNode();
        n.PopulateOnDemand = true;
        e.Node.ChildNodes.Add(n);
        if (...) // condition for nodes i want expand
            n.Expand(); // it calls resursively by treeview
    }

and it expand tree on server and send all nodes to client in 1 request (ExpandToNodes functionality). This doesnt work with WebTreeView. I can call n.Expand() on WebTreeView1_InitializeChildNodes but nothing happend - i know its not asp:TreeView, just asking if there is better way than "clicking" with javascript on nodes and generate many requests.

Another thing i notice is if I expand node (populateOnDemand) and it has no child the "plus" button didnt hide and also clientside event OnNodeExpand is not called (but this is maybe OK, nothing expanded)

Thanks

Hello,

Thank you for the reply.

Basically, in “Load on Demand” case, that is behavior in WebTreeView, you should load/render the parent node before you can load the child node.

Regarding “the better workaround”, I still can’t get the better workaround than yours.

Regarding “hide plus button”, perhaps you could hide the “plus” / expand button in “OnInitializeNode” server side event.

Here’s the example snippet code how to hide the expand button:

protected void WebTreeView1_InitializeNode(object sender, WebTreeViewNodeEventArgs e){
    // For example, this code will hide the node the have depth level equal to 3
    if (e.Node.Depth == 3)
        e.Node.ChildNodeExpandable = false;
}

Thank you.

Regards,
Hans K.