asp telerik treeView throws an exception when trying to renderControl

Question

I am working on a TreeView and have to execute the renderControl() method. When it fires, it gives an exception: InvalidOperationException: Page cannot be null. Please ensure that this operation is being performed in the context of an ASP.NET request.

I have the following code when will comment where the error is:

try{
   StringWriter writer = new StringWriter();
   HtmlTextWriter tOut = new HtmlTextWriter(writer);
   ddFieldFilter.RenderControl(tOut);  //This doesnt error.
   tvFields = new RadTreeView();
   tvFields.NodeExpand += new RadTreeViewEventHandler(tvFields_NodeExpand);
   tvFields.NodeClick += new RadTreeViewEventHandler(tvFields_NodeClick);
   startTree();
   tvFields.RenderControl(tOut);  //Errors here.
   String context = writer.toString();
}catch(Exception e){
   throw new Exception("Error Loading Page: " + e.Message);
}

Do you think it might be because there is currently content in the writer? I was thinking to clear or flush it to the string and then rebuild it. I wasnt sure it would append onto the current buffer

Let me know if you need additional Information

Answer 1

What you're trying to do doesn't look like it is currently supported. Although this question is in regards to the Asp.NET ColorPicker control, I believe it applies to the RadTreeView control as well.

Via the Telerik Support Center:

Q: Is there any way to get the ColorPicker to render without a page? I had to add it in a situation where I write directly in the aspx, not aspx.cs. Also, I might need to do it from a generic handler, ashx. Is this possible?

A: The control needs to be added to a page, either in its markup, or in its code-behind. You could try the RenderControl method and write to Response.OutputStream, yet this is not a supported scenario and it success cannot be guaranteed, so I advise against such attempts.

Regards,
Marin
the Telerik team