.NET微信公众号开发之查询自定义菜单

 /// <summary>
 /// 微信许可令牌
 /// </summary>
 public class AccessToken
 {
 /// <summary>
 /// 保存已获取到的许可令牌，键为公众号，值为公众号最后一次获取到的令牌
 /// </summary>
 private static ConcurrentDictionary<string, Tuple<AccessToken, DateTime>> accessTokens = new ConcurrentDictionary<string, Tuple<AccessToken, DateTime>>();

 /// <summary>
 /// 获取access token的地址
 /// </summary>
 private const string urlForGettingAccessToken = "https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid={0}&secret={1}";
 /// <summary>
 /// 获取access token的http方法
 /// </summary>
 private const string httpMethodForGettingAccessToken = WebRequestMethods.Http.Get;
 /// <summary>
 /// 保存access token的最长时间（单位：秒），超过时间之后，需要重新获取
 /// </summary>
 private const int accessTokenSavingSeconds = 7000;

 /// <summary>
 /// access token
 /// </summary>
 public string access_token { get; set; }
 /// <summary>
 /// 有效时间，单位：秒
 /// </summary>
 public int expires_in { get; set; }

 /// <summary>
 /// 构造函数
 /// </summary>
 /// <param name="_access_token">access token</param>
 /// <param name="_expires_in">有效时间</param>
 internal AccessToken(string _access_token, int _expires_in)
 {
 access_token = _access_token;
 expires_in = _expires_in;
 }

 /// <summary>
 /// 返回AccessToken字符串
 /// </summary>
 /// <returns></returns>
 public override string ToString()
 {
 return string.Format("AccessToken：{0}\r\n有效时间：{1}秒", access_token, expires_in);
 }

 /// <summary>
 /// 从JSON字符串解析AccessToken
 /// </summary>
 /// <param name="json">JSON字符串</param>
 /// <returns>返回AccessToken</returns>
 internal static AccessToken ParseFromJson(string json)
 {
 var at = JsonConvert.DeserializeAnonymousType(json, new { access_token = "", expires_in = 1 });
 return new AccessToken(at.access_token, at.expires_in);
 }

 /// <summary>
 /// 尝试从JSON字符串解析AccessToken
 /// </summary>
 /// <param name="json">JSON字符串</param>
 /// <param name="msg">如果解析成功，返回AccessToken；否则，返回null。</param>
 /// <returns>返回是否解析成功</returns>
 internal static bool TryParseFromJson(string json, out AccessToken token)
 {
 bool success = false;
 token = null;
 try
 {
 token = ParseFromJson(json);
 success = true;
 }
 catch { }
 return success;
 }

 /// <summary>
 /// 得到access token
 /// </summary>
 /// <param name="userName">公众号</param>
 /// <returns>返回access token</returns>
 public static AccessToken Get(string userName)
 {
 Tuple<AccessToken, DateTime> lastToken = accessTokens.ContainsKey(userName) ? accessTokens[userName] : null;
 AccessToken token = lastToken == null ? null : lastToken.Item1;
 DateTime refreshTime = lastToken == null ? DateTime.MinValue : lastToken.Item2;
 double ms = (DateTime.Now - refreshTime).TotalSeconds;
 if (ms > accessTokenSavingSeconds || token == null)
 {
 //尝试从微信服务器获取2次
 ErrorMessage msg;
 AccessToken newToken = GetFromWeixinServer(userName, out msg);
 if (newToken == null)
 newToken = GetFromWeixinServer(userName, out msg);
 if (newToken != null)
 {
 lastToken = new Tuple<AccessToken, DateTime>(newToken, DateTime.Now);
 accessTokens[userName] = lastToken;
 token = newToken;
 }
 }
 return token;
 }

 /// <summary>
 /// 从微信服务器获取access token
 /// </summary>
 /// <param name="userName">公众号</param>
 /// <param name="msg">从服务器返回的错误信息。</param>
 /// <returns>返回许可令牌；如果获取失败，返回null。</returns>
 private static AccessToken GetFromWeixinServer(string userName, out ErrorMessage msg)
 {
 AccessToken token = null;
 msg = new ErrorMessage(ErrorMessage.ExceptionCode, "");
 string url = string.Format(urlForGettingAccessToken, WxPayConfig.APPID, WxPayConfig.APPSECRET);
 string result;
 if(!HttpHelper.Request(url, out result, httpMethodForGettingAccessToken, string.Empty))
 {
 msg.errmsg = "从微信服务器获取响应失败。";
 return token;
 }
 if (ErrorMessage.IsErrorMessage(result))
 msg = ErrorMessage.Parse(result);
 else
 {
 try
 {
 token = AccessToken.ParseFromJson(result);
 }
 catch (Exception e)
 {
 msg = new ErrorMessage(e);
 }
 }
 return token;
 }
 }