/// <summary>
 /// 读取request中的user-agent识别出浏览器版本号
 /// </summary>
 /// <param name="request"></param>
 /// <returns></returns>
 public static string GetBrowserVersion(this HttpRequest request)
 {
     return(ComFunc.GetBrowserVersion(ComFunc.nvl(request.Headers["user-agent"])));
 }