private void Render()
{
List<TreeElement> items = (List<TreeElement>)ViewState[ClientTreeItems];
if(items == null) return;
StringBuilder sb = new StringBuilder();
sb.Append(@"<div class=""treecontainer"">");
int iteration = 0;
RenderSubTree(items, sb, ref iteration);
sb.Append("</div>");
lblContent.Text = sb.ToString();
}