gridview 导出excel代码，以及关于乱码问题

/// <param name="FileType">文件类型：application/ms-excel</param>
        /// <param name="FileName">文件名字</param>
        /// <param name="gridview"></param>
        public static void ExportToExcel(this Page _page, string FileType, string FileName, GridView gridview)
        {
            _page.Response.Clear();
            _page.Response.Buffer = true;
            _page.Response.Charset = "utf-8";
            _page.Response.ContentEncoding = System.Text.Encoding.GetEncoding("utf-8");
             _page.Response.AppendHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(FileName, System.Text.Encoding.UTF8).ToString());
            _page.Response.ContentType = FileType;

　　　　////这行很重要，是解决乱码的关键之所在。
            _page.Response.Write("<meta http-equiv=Content-Type content=/"text/html; charset=utf-8/">");  

            _page.EnableViewState = false;
            StringWriter tw = new StringWriter();
            HtmlTextWriter hw = new HtmlTextWriter(tw);
            gridview.RenderControl(hw);
            _page.Response.Output.Write(tw.ToString());
            _page.Response.Flush();
            _page.Response.End();
        }

最初尝试各种办法，换各种编码，偶尔还是有gridview会出现乱码。原因是各个gridview的stream不一样，编码或许会出现问题。

最终还是靠加粗的那行代码，解决了问题。