微信公众平台，网页授权及 40029 问题解决

1、跳转授权链接

https://open.weixin.qq.com/connect/oauth2/authorize?appid=xxx&redirect_uri=xxx&response_type=code&scope=snsapi_userinfo&state=STATE&connect_redirect=1#wechat_redirect

&connect_redirect=1 这个参数，刚开始没有加，总是报 {'errcode':40029,'errmsg':'invalid code, hints: [ req_id: 0407ns44 ]'} 这个错误 ，调试时发现会访问两次，一次是301，页面重定向了，第二次跟第一次就差这个参数。加上后，不再报错。code 可以了。

二需要注意的是 redirect_uri = xxx 需要自己URL转码

2、获取用户信息，直接上代码。

<%@ WebHandler Language="C#" Class="getinfos" %>

using System;
using System.Web;
using Newtonsoft.Json.Linq;
using System.Net;
using System.IO;
using System.Text;

public class getinfos : IHttpHandler {
    
    public void ProcessRequest (HttpContext context) {
        //一切都从这里开始
        string code = context.Request["code"].ToString();
        
        context.Response.ContentType = "text/plain";
        context.Response.Write(GetInfos(code));
    }
 
    public bool IsReusable {
        get {
            return false;
        }
    }

    public string GetInfos(string _code)
    {
        //
        string _access_tokens = GetToken(_code);
        JObject json = JObject.Parse(_access_tokens);        
        string access_token = json["access_token"].ToString();
        string refresh_token = json["refresh_token"].ToString();
        string openid = json["openid"].ToString();
        
        //
        string _infos = GetUserInfo(access_token, openid);
        JObject info = JObject.Parse(_infos);

        if (info["errcode"] != null)
        {       
            _access_tokens = RefreshToken(refresh_token);
            json = JObject.Parse(_access_tokens);
                        
            access_token = json["access_token"].ToString();
            openid = json["openid"].ToString();

            _infos = GetUserInfo(access_token, openid);
        }

        return _infos;
    }

    /// <summary>
    /// 用code 获取 Token
    /// </summary>
    private string GetToken(string _code)
    {
        if (_code.IndexOf(""") > -1)
            _code = _code.Replace(""", "");
        
        string URL = "https://api.weixin.qq.com/sns/oauth2/access_token";
        string RequestPara = "?appid=xxx";
        RequestPara += "&secret=xxx";
        RequestPara += "&code=" + _code;
        RequestPara += "&grant_type=authorization_code";

        string _access_tokens = GetData(URL, RequestPara);
        _access_tokens = _access_tokens.Replace(""", "'");

        return _access_tokens;
    }

    /// <summary>
    /// 获取用户信息
    /// </summary>
    private string GetUserInfo(string access_token, string openid)
    {
        if (access_token.IndexOf(""") > -1)
            access_token = access_token.Replace(""", "");

        if (openid.IndexOf(""") > -1)
            openid = openid.Replace(""", "");
        
        string I_URL = "https://api.weixin.qq.com/sns/userinfo";
        string I_RequestPara = "?access_token=" + access_token;
        I_RequestPara += "&openid=" + openid;
        I_RequestPara += "&lang=zh_CN";

        string _infos = GetData(I_URL, I_RequestPara);
        _infos = _infos.Replace(""", "'");

        return _infos;
    }

    /// <summary>
    /// 刷新 Token
    /// </summary>
    private string RefreshToken(string refresh_token)
    {
        if (refresh_token.IndexOf(""") > -1)
            refresh_token = refresh_token.Replace(""", "");
        
        string R_URL = "https://api.weixin.qq.com/sns/oauth2/refresh_token";
        string R_RequestPara = "?appid=xxx";
        R_RequestPara += "&grant_type=refresh_token";
        R_RequestPara += "&refresh_token=" + refresh_token;
        
        string _infos = GetData(R_URL, R_RequestPara);
        _infos = _infos.Replace(""", "'");

        return _infos;
    }

    /// <summary>
    /// 访问地址，并获取数据
    /// </summary>
    private string GetData(string URL, string RequestPara)
    {
        RequestPara = RequestPara.IndexOf('?') > -1 ? (RequestPara) : ("?" + RequestPara);

        WebRequest hr = HttpWebRequest.Create(URL + RequestPara);
        byte[] buf = System.Text.Encoding.GetEncoding("utf-8").GetBytes(RequestPara);
        hr.Method = "GET";

        System.Net.WebResponse response = hr.GetResponse();
        StreamReader reader = new StreamReader(response.GetResponseStream(), Encoding.GetEncoding("utf-8"));
        string ReturnVal = reader.ReadToEnd();
        reader.Close();
        response.Close();

        return ReturnVal;
    }
}