Hi.

The root ID is always "-1" (that's the Constants.System.Root).

If you open a sub-tree, it isn't already available in the backoffice but is requested via an async request (just look in the dev tools).

The request calls your GetTreeNodes() method with the id parameter you have clicked on.

So every time GetTreeNodes() is called, you can only return ONE level of hierarchy. That's why your CreateTreeNodes() aren't creating a nested tree.

What you have to do is the following. Divide your method into ID groups, so you can return the correct trees.

I have altered your code like this:

protected override TreeNodeCollection GetTreeNodes(string id, System.Net.Http.Formatting.FormDataCollection queryStrings)
{
  var nodes = new TreeNodeCollection();

  // render top-level tree (for id = -1)
  if (id == Constants.System.Root.ToInvariantString())
  {
      foreach (var opco in opCoService.GetAll(c => c.Brands))
      {
          var node = CreateTreeNode(opco.Id.ToString(), Constants.System.Root.ToString(), queryStrings, opco.CompanyName, "icon-folder", false);
          nodes.Add(node);
      }
  }
  // render sub-tree if id != -1
  else 
  {
    // this line is pseudo-code, as I don't know how your service looks like
    // but you'll get the idea ;-)
    var opco = opCoService.GetById(id);

    if (opco != null && opco.Brands.Any())
    {
        foreach (var brand in opco.Brands)
        {
            var childNode = CreateTreeNode(brand.Id.ToString(), opco.Id.ToString(), queryStrings, brand.BrandName);
            nodes.Add(childNode);
        }
    }
  }

  return nodes;
}

If you have more than two levels in your tree you could (just an idea) also add a prefix to the id, like so:

var node = CreateTreeNode("opco-" + opco.Id.ToString(), Constants.System.Root.ToString(), queryStrings, opco.CompanyName, "icon-folder", false);

var childNode = CreateTreeNode("brand-" + brand.Id.ToString(), "opco-" + opco.Id.ToString(), queryStrings, brand.BrandName);

This will give you the ability to check if the ID is from a brand, opco and so on.

if (id.StartsWith("opco-")) ... // output brand tree
else if (id.StartsWith("brand-")) ... // output sub-nodes of a brand
// ... and so on