private void RetriveStock()
    {
        string constr = ConfigurationManager.ConnectionStrings["ConnectionString_master"].ConnectionString;

        using (SqlConnection conn = new SqlConnection(constr))
        {
            using (SqlCommand cmd = new SqlCommand("ClosingStock_WebPortal"))
            {
                cmd.CommandType = CommandType.StoredProcedure;
                cmd.Parameters.AddWithValue("@deponame", DropDownstocklocation.SelectedValue);


                using (SqlDataAdapter sda = new SqlDataAdapter())
                {
                    cmd.Connection    = conn;
                    sda.SelectCommand = cmd;
                    using (DataTable dt = new DataTable())
                    {
                        sda.Fill(dt);
                        Grid_stockdetails.DataSource = dt;
                        Grid_stockdetails.DataBind();
                        //Calculate Sum and display in Footer Row
                        decimal total = dt.AsEnumerable().Sum(row => row.Field <decimal>("Stock Value"));
                        Grid_stockdetails.FooterRow.Cells[9].Text            = "Total";
                        Grid_stockdetails.FooterRow.Cells[9].HorizontalAlign = HorizontalAlign.Right;
                        Grid_stockdetails.FooterRow.Cells[10].Text           = total.ToString("N2");
                    }
                }
            }
        }
    }
    protected void exportbtn_Click(object sender, EventArgs e)
    {
        if (Grid_stockdetails.Rows.Count != 0)
        {
            Response.Clear();
            Response.Buffer = true;
            //Response.ContentType = "application/application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
            //Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
            //Response.AppendHeader("content-disposition", "attachment; filename=GridViewExport.xlsx");

            Response.AddHeader("content-disposition", "attachment;filename=Stock Report " + DateTime.Now.Date + ".xls");
            Response.Charset = "";

            Response.ContentType = "application/vnd.ms-excel";
            StringWriter   sw = new StringWriter();
            HtmlTextWriter hw = new HtmlTextWriter(sw);
            Grid_stockdetails.RenderControl(hw);
            //Response.Write(style);
            Response.Output.Write(sw.ToString());
            Response.Flush();
            Response.End();
        }
    }