多个GRIDVIEW同时导入到一个EXCEL文件中

HttpContext.Current.Response.Clear();
        Response.Buffer = false;
        HttpContext.Current.Response.Charset = "GB2312";
        HttpContext.Current.Response.ContentEncoding = System.Text.Encoding.UTF7;
        HttpContext.Current.Response.ContentType = "application/ms-excel";
        HttpContext.Current.Response.AppendHeader("Content-Disposition", "attachment;filename=11.xls");
        System.IO.StringWriter tw = new System.IO.StringWriter();
        HtmlTextWriter hw = new HtmlTextWriter(tw);
        GVsystemzhuangbei.Columns[4].Visible = false;
        GVsystemzhuangbei.Columns[5].Visible = false;
        GVsystemzhuangbei.RenderControl(hw);

        GVsystemzhuangzhi.Columns[6].Visible = false;
        GVsystemzhuangzhi.Columns[7].Visible = false;
        GVsystemzhuangzhi.RenderControl(hw);

        GVzhongxinzhan.Columns[5].Visible = false;
        GVzhongxinzhan.Columns[6].Visible = false;
        GVzhongxinzhan.RenderControl(hw);

GVchuanganqi.Columns[7].Visible = false;
        GVchuanganqi.Columns[8].Visible = false;
        GVchuanganqi.RenderControl(hw);
        HttpContext.Current.Response.Write(tw.ToString());
        HttpContext.Current.Response.End();