Treeview RenderControl Error

[Prakash V]

Hi all,

i am trying to render a treeview control and send the HTML output
to some other method, but it gives NullReferenceException, i tried many ways
but could not solve this issue. if i add the control directly to page it
works but gives error while using RenderControl.
my code & stack trace

private string RenderTree()
{
TreeView Tview = new TreeView();
TreeNode tnode = new TreeNode("Node1", "1");
Tview.Nodes.Add(tnode);
Tview.ID = "Tree1";
StringBuilder sb = new StringBuilder();
StringWriter sw = new StringWriter(sb);
HtmlTextWriter htmlTW = new HtmlTextWriter(sw);
Tview.RenderControl(htmlTW);
return sb.ToString();
}

[NullReferenceException: Object reference not set to an instance of an
object.]
System.Web.UI.Control.get_SpacerImageUrl() +50
System.Web.UI.WebControls.TreeView.RenderBeginTag(HtmlTextWriter writer)
+202
System.Web.UI.WebControls.WebControl.Render(HtmlTextWriter writer) +31
System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer,
ControlAdapter adapter) +74
System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter
adapter) +291
System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +49
TreeviewRender.RenderTree() in
d:\TestProject\TestProject\TreeviewRender.aspx.cs:30
TreeviewRender.Page_Load(Object sender, EventArgs e) in
d:\TestProject\TestProject\TreeviewRender.aspx.cs:17
System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o,
Object t, EventArgs e) +31
System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender,
EventArgs e) +68
System.Web.UI.Control.OnLoad(EventArgs e) +88
System.Web.UI.Control.LoadRecursive() +74
System.Web.UI.Page.ProcessRequestMain(Boolean
includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3030


Thanks in Advance,
Prakash.V