Control 'GridView1' of type 'GridView' must be placed inside a form tag with runat=server.

I ran across this error when trying to export the grid view data to excel.
I do have a form tag setup runat=server. But it continue to fail.

Solution: Create an HtmlForm object and add the grid view to the form in code.

string style = @" ";

           Response.ClearContent();

           // Create form tag

           HtmlForm form1 = new HtmlForm();

           form1.Controls.Add(gvData);

           Response.AddHeader("content-disposition", "myfilename.xls");

           Response.ContentType = "application/excel";

           StringWriter sw = new StringWriter();
           StringWriter header= new StringWriter();

          
           HtmlTextWriter htw = new HtmlTextWriter(sw);

           gvData.RenderControl(htw);
          

           // Style is added dynamically

           Response.Write(style);

           Response.Write(sw.ToString());

           Response.End();