Export to Excel with child grid in .Net

DataSet dsParent = new System.Data.DataSet();

            //export to excel with allow paging =false

            Response.Clear();

            //parent grid

            grvFetchJobPosting.AllowPaging = false;

            Response.Buffer = true;

            GridView gvrChild = new GridView();

            System.IO.StringWriter oStringWriter = new System.IO.StringWriter();

            System.Web.UI.HtmlTextWriter oHtmlTextWriter = new System.Web.UI.HtmlTextWriter(oStringWriter);

            dsParent = (DataSet)Session["FetchVMSData"];

            grvFetchJobPosting.AllowPaging = false;

            grvFetchJobPosting.DataSource = dsParent.Tables[0];

            grvFetchJobPosting.DataBind();

            HtmlForm frm = new HtmlForm();

            foreach (GridViewRow gvr in grvFetchJobPosting.Rows)

            {

                if (gvr.RowType == DataControlRowType.DataRow)

                {

                    GridView GridView2 = (GridView)gvr.FindControl("grvVendorData");//child grid view

                    GridView2.AllowPaging = false;

                }

            }

            Response.ContentType = "application/vnd.ms-excel";

            Response.AddHeader("Content-Disposition", "attachment;filename=SalesReport.xls");

            //Response.Headers["Content-Disposition"] = "attachment;filename=DetailedRRFReport.xls";

            Response.Charset = "";

            this.EnableViewState = false;

            this.ClearControls(grvFetchJobPosting);

            grvFetchJobPosting.RenderControl(oHtmlTextWriter);

            grvFetchJobPosting.Parent.Controls.Add(frm);

            frm.Attributes["runat"] = "server";

            //frm.Controls.Add(FetchRRFDataGrid);

            frm.RenderControl(oHtmlTextWriter);

            Response.Write(oStringWriter.ToString());

            Response.End();