Dispaly gridview data in html format

This is c-sharpcode and have you stored the datatable in ViewState. If not,please add. Check it once.

its not displaying anything..

Please try the below code.

private void Export(GridView ActiveProductsGrid)
        {
           
            string result = null;

            Response.Clear();
            Response.ContentType = "text/HTML";

            using (var stringWriter = new StringWriter())
            {
                using (var htmlWriter = new HtmlTextWriter(stringWriter))
                {
                    htmlWriter.RenderBeginTag(HtmlTextWriterTag.Html);
                    htmlWriter.RenderBeginTag(HtmlTextWriterTag.Body);
                    htmlWriter.RenderBeginTag(HtmlTextWriterTag.Form);
                    var dg = new DataGrid { DataSource = (DataTable)ViewState["ProductTable"] };
                    dg.DataBind();
                    dg.RenderControl(htmlWriter);
                    htmlWriter.RenderEndTag();
                    htmlWriter.RenderEndTag();
                    htmlWriter.RenderEndTag();

                }
                // output the html
                result = stringWriter.ToString();
                Response.Write(result);
            }
            Response.Flush();
            Response.End();

            

        }

i want export gridview data into html format

Do you want to display some HTML contents inside gridview ? 
Do you want export the gridview data into HTML format?