浏览器下载文件名称乱码问题

//火狐浏览器不需要将中文文件名进行编码格式转换

if (Request.ServerVariables["http_user_agent"].ToLower().IndexOf("firefox") == -1)

        {
            fileName = HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8);

        }

2

        HttpBrowserCapabilities brObject = Request.Browser;
        string browserName = brObject.Type;
        fileName = HttpUtility.UrlEncode(string.Format("{1}", System.DateTime.Now, filename));