asp.net 将dt转换成excel 在线下载

      private StringWriter GetStringWriter(DataTable dt)
        {
            StringWriter sw = new StringWriter();
            //读列名  
            foreach (DataColumn dc in dt.Columns)
                sw.Write(dc.ColumnName + "\t");
            //读列值  
            //重新的一行  
            sw.Write(sw.NewLine);
            if (dt != null)
            {
                foreach (DataRow dr in dt.Rows)
                {
                    for (int i = 0; i < dt.Columns.Count; i++)
                    {
                        sw.Write(dr[i].ToString() + "\t");
                    }
                    sw.Write(sw.NewLine);
                }
            }
            sw.Close();

            return sw;
        }

        protected void ExcelImport(DataTable dt, string ExportFileName)
        {
            StringWriter sw = GetStringWriter(dt);
            //当前编码  
            HttpContext.Current.Response.ContentEncoding = System.Text.Encoding.GetEncoding("GB2312");
            //把输出的文件名进行编码  
            string fileName = HttpUtility.UrlEncode(ExportFileName, System.Text.Encoding.UTF8);
            //文件名  
            string str = "attachment;filename=" + fileName + ".xls";
            //把文件头输出，此文件头激活文件下载框  
            HttpContext.Current.Response.AppendHeader("Content-Disposition", str);//http报头文件  
            HttpContext.Current.Response.ContentType = "application/ms-excel";
            this.Page.EnableViewState = false;
            Response.Write(sw);
            Response.End();
        }  

            string sql = "select * from eco_sys_members ";
            DataTable dt = DbHelperSQL.Query(sql).Tables[0];
            if (dt.Rows.Count > 0)
            {
                //导出Excel  
                ExcelImport(dt, DateTime.Now.ToString());

            }