GridView Data downlod into Excel and Pdf file

protected void btnExpExcel_Click(object sender, EventArgs e)
        {
            Response.ClearContent();
            Response.Buffer = true;
            Response.AddHeader("content-disposition", string.Format("attachment; filename={0}", "Report.xls"));
            Response.ContentType = "application/ms-excel";
 
            StringWriter sw = new StringWriter();
            HtmlTextWriter htw = new HtmlTextWriter(sw);
 
            DataTable dt = new DataTable();
            dt = (DataTable)Session["dtReport"];
 
            gvMISReport.AllowPaging = false;
 
            gvMISReport.DataSource = dt;
            gvMISReport.DataBind();
 
            //Change the Header Row back to white color
            gvMISReport.HeaderRow.Style.Add("background-color", "#FFFFFF");
            
            //Applying stlye to gridview header cells
            for (int i = 0; i < gvMISReport.HeaderRow.Cells.Count; i++)
            {
                gvMISReport.HeaderRow.Cells[i].Style.Add("background-color", "#157CB0");
            }
            int j = 1;
            
            //This loop is used to apply stlye to cells based on particular row
            foreach (GridViewRow gvrow in gvMISReport.Rows)
            {
                gvrow.BackColor = Color.White;
                if (j <= gvMISReport.Rows.Count)
                {
                    if (j % 2 != 0)
                    {
                        for (int k = 0; k < gvrow.Cells.Count; k++)
                        {
                            gvrow.Cells[k].Style.Add("background-color", "#EFF3FB");
                        }
                    }
                }
                j++;
            }
            gvMISReport.RenderControl(htw);
            Response.Write(sw.ToString());
            Response.End();
        }