Try to add the exporter as a Global  variable of the form and create and add it from the CreateChildControls or CreateControls event of the form... I am working with Web Parts and I have to override the RenderControl event of the form, if you do this too be sure you are render the Exporter control in this event.

        protected override void CreateChildControls()
        {
            base.CreateChildControls();

            excelExporter = new UltraWebGridExcelExporter("ExcelExporter");
            this.Controls.Add(excelExporter);

        }

  public override void RenderControl(HtmlTextWriter writer)
        {
            this.excelExporter.RenderControl(writer);

        }

Sivaprasad,

 I had a similar issue with the PDF export. It turns out in my case it was related to the path of a CSS file in the master page. It seems the exporter cannot resolve the path although it works fine in the app.

I changed mine so that the path is resolved and this exporter works fine now. A sample of the pathing is below. The key is the Page.ResolveUrl

 <link href="<%= Page.ResolveUrl("~")%>style/appstyle.css" rel="stylesheet" type="text/css" />

HTH

Brad

If you still get the error when you add the WebGridDocumentExporter to the form's Controls collection in code, then this may be a bug - or there may be something specific about the application setup where an error like this would be expected.  Can you reproduce this in an isolated sample application?  If so, please submit a support request so that a Developer Support Engineer can investigate this further.

What happens if you have the WebGridDocumentExporter added to your page at design-time, rather than at run-time?

Since you're dynamically creating your WebGridDocumentExporter control, try adding it to your page after you create it but before you call its Export() method:

this.Form1.Controls.Add(exp);