C# 微信access_token缓存和过时刷新

摘自：http://blog.csdn.net/hechurui/article/details/22398849

首先创建一个Access_token类

/// <summary>
///Access_token 的摘要说明
/// </summary>
public class Access_token
{
    public Access_token()
    {
        //
        //TODO: 在此处添加构造函数逻辑
        //
    }
    string _access_token;
    string _expires_in;

    /// <summary>
    /// 获取到的凭证
    /// </summary>
    public string access_token
    {
        get { return _access_token; }
        set { _access_token = value; }
    }

    /// <summary>
    /// 凭证有效时间，单位：秒
    /// </summary>
    public string expires_in
    {
        get { return _expires_in; }
        set { _expires_in = value; }
    }
}

用下面的XML文件来存放access_token，创建一个XMLFile.xml，把Access_YouXRQ标签的内容写成一个已通过去的时间，这样咱们好在一开始调用的时候，发现已通过期，而后获取新的access_token。

<?xml version="1.0" encoding="utf-8"?>
<xml>
  <Access_Token>初始值能够随便写</Access_Token>
  <Access_YouXRQ>1980/12/12 16:06:38</Access_YouXRQ>
</xml>

改造一下以前得到Access_token的方法，让他给Access_token实例赋值

public static Access_token GetAccess_token()
    {
        string appid = 你的appid ;
        string secret = 你的secret;
        string strUrl = "https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid=" + appid + "&secret=" + secret;
        Access_token mode = new Access_token();

        HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create(strUrl);

        req.Method = "GET";
        using (WebResponse wr = req.GetResponse())
        {
            HttpWebResponse myResponse = (HttpWebResponse)req.GetResponse();

            StreamReader reader = new StreamReader(myResponse.GetResponseStream(), Encoding.UTF8);

            string content = reader.ReadToEnd();
            //Response.Write(content);
            //在这里对Access_token 赋值
            Access_token token = new Access_token();
            token = JsonHelper.ParseFromJson<Access_token>(content);
            mode.access_token = token.access_token;
            mode.expires_in = token.expires_in;
        }
        return mode;
    }

以上的方法用到了Json对象的处理，因此我把JsonHelper的代码一贴出来供你们参考，一下就是JsonHelper.cs的代码：

using System;
using System.IO;
using System.Text;
using System.Runtime.Serialization.Json;



public class JsonHelper
{
    /// <summary>
    /// 生成Json格式
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="obj"></param>
    /// <returns></returns>
    public static string GetJson<T>(T obj)
    {
        DataContractJsonSerializer json = new DataContractJsonSerializer(obj.GetType());
        using (MemoryStream stream = new MemoryStream())
        {
            json.WriteObject(stream, obj);
            string szJson = Encoding.UTF8.GetString(stream.ToArray()); return szJson;
        }
    }
    /// <summary>
    /// 获取Json的Model
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="szJson"></param>
    /// <returns></returns>
    public static T ParseFromJson<T>(string szJson)
    {
        T obj = Activator.CreateInstance<T>();
        using (MemoryStream ms = new MemoryStream(Encoding.UTF8.GetBytes(szJson)))
        {
            DataContractJsonSerializer serializer = new DataContractJsonSerializer(obj.GetType());
            return (T)serializer.ReadObject(ms);
        }
    }
}

咱们还须要些一个判断access_token是否过时若是过时更新XML文件的方法。

/// <summary>
    /// 根据当前日期 判断Access_Token 是否超期  若是超期返回新的Access_Token   不然返回以前的Access_Token
    /// </summary>
    /// <param name="datetime"></param>
    /// <returns></returns>
    public static string IsExistAccess_Token()
    {

        string Token = string.Empty;
        DateTime YouXRQ;
        // 读取XML文件中的数据，并显示出来 ，注意文件路径
        string filepath = Server.MapPath("XMLFile.xml");

        StreamReader str = new StreamReader(filepath, System.Text.Encoding.UTF8);
        XmlDocument xml = new XmlDocument();
        xml.Load(str);
        str.Close();
        str.Dispose();
        Token = xml.SelectSingleNode("xml").SelectSingleNode("Access_Token").InnerText;
        YouXRQ = Convert.ToDateTime(xml.SelectSingleNode("xml").SelectSingleNode("Access_YouXRQ").InnerText);

        if (DateTime.Now > YouXRQ)
        {
            DateTime _youxrq = DateTime.Now;
            Access_token mode = GetAccess_token();
            xml.SelectSingleNode("xml").SelectSingleNode("Access_Token").InnerText = mode.access_token;
            _youxrq = _youxrq.AddSeconds(int.Parse(mode.expires_in));
            xml.SelectSingleNode("xml").SelectSingleNode("Access_YouXRQ").InnerText = _youxrq.ToString();
            xml.Save(filepath);
            Token = mode.access_token;
        }
        return Token;
    }

好了，完成了上面的工做，我只须要在使用到access_token的时以下调用就OK了，“客户不再用担忧token的过时”。
string _access_token = IsExistAccess_Token();