asp.net ashx导出excel到前台

最近有一个项目使用以前的ashx，不能使用FileResult，只有通过response返回拼接好的字符串。但是通过查阅资料拼接的字符串总是提示文件格式不匹配，虽然能正常打开，但是体验很不好，在此总结一下我的解决方法：
直接下载excel会提示格式不相符，稍微修改，下载成csv的就没问题了

• 后台：

/// <summary>  
/// DataTable导出到Excel  
/// </summary>  
/// <param name="dt">DataTable类型的数据源</param>  
/// <param name="FileType">文件类型</param>  
/// <param name="FileName">文件名</param>  
public void CreateExcel(HttpContext context, List<PB_SITE_BASIC> siteList, string FileName)
{
	//分割符
	string split = ",";

	HttpResponse Response = System.Web.HttpContext.Current.Response;
	Response.Clear();
	Response.Charset = "UTF-8";
	Response.Buffer = true;
	Response.ContentEncoding = System.Text.Encoding.GetEncoding("GB2312");
	Response.AppendHeader("Content-Disposition", "attachment;filename="" + System.Web.HttpUtility.UrlEncode(FileName, System.Text.Encoding.UTF8) + ".csv"");
	Response.ContentType = "application/ms-excel";
	string colHeaders = string.Empty;
	string ls_item = string.Empty;

	int i = 0;
	int cl = siteList.Count;

	//添加表头
	ls_item += "站点编号" + split;
	ls_item += "站点名称" + split;
	ls_item += "车桩总数" + split;
	ls_item += "基站地址" + split;
	ls_item += "所属区域" + split;
	ls_item += "站点地址" + split;
	ls_item += "站点纬度" + split;
	ls_item += "站点经度" + split;

	ls_item = ls_item.Substring(0, ls_item.Length - 1) + "
";

	foreach (var site in siteList)
	{
		ls_item += site.SID.ToString() + split;
		ls_item += site.NAME.ToString() + split;
		ls_item += site.CAPACITY.ToString() + split;
		ls_item += site.BASESTATION_ID.ToString() + split;
		ls_item += site.REGION_ID.ToString() + split;
		ls_item += site.ADDRESS.ToString() + split;
		ls_item += site.LAT.ToString() + split;
		ls_item += site.LNG.ToString() + split;
		ls_item += "
";

		Response.Output.Write(ls_item);
		ls_item = string.Empty;
	}
	Response.Output.Flush();
	Response.End();
}

• 前台

//导出
$("#btExport").click(function () {
 window.location = "ExportSiteBasic.ashx";
});