1         //记录access token 申请时的时间
 2         private static DateTime GetAccessToken_Time;  
 3         /// <summary>
 4         /// 过期时间为7200秒
 5         /// </summary>
 6         private static int Expires_Period = 7200;

 　　　　　　private static string mAccessToken;
 7         /// <summary>
 8         /// 获取access token
 9         /// </summary>
10         /// <returns></returns>
11         private static string GetAccessToken()
12         {
13             if (string.IsNullOrEmpty(mAccessToken) || HasExpired())
14             {
15                 string Url = "https://api.weixin.qq.com/cgi-bin/token";
16                 string RequestPara = "grant_type=client_credential&appid=" + APPID + "&secret=" + APPSECRET;
17                 string result = WebRequestHelper.GetData(RequestPara, Url);
18                 if (!result.Equals(""))
19                 {
20                     GetAccessToken_Time = DateTime.Now;
21                     accesstoken token = JsonFormat.Deserialize<accesstoken>(result);
22                     Expires_Period = Convert.ToInt32(token.expires_in);
23                     return token.access_token;
24                 }
25                 else
26                 {
27                     GetAccessToken_Time = DateTime.MinValue;
28                 }
29             }
30             return null;
31         }
32 
33         /// <summary>
34         /// 判断Access_token是否过期
35         /// </summary>
36         /// <returns>bool</returns>
37         private static bool HasExpired()
38         {
39             if (GetAccessToken_Time != null)
40             {
41                 //过期时间，允许有一定的误差，一分钟。获取时间消耗
42                 if (DateTime.Now > GetAccessToken_Time.AddSeconds(Expires_Period).AddSeconds(-60))
43                 {
44                     return true;
45                 }
46             }
47             return false;
48         }