添加引用：
using System.Web.Script.Serialization;
using System.Collections.Generic;
using Jayrock.Json;
public void GetInfos() {
var code = Request.QueryString["code"];
string json = string.Empty;
string url = "https://api.weixin.qq.com/sns/oauth2/access_token?appid=" + appid + "&secret=" + secret + "&code=" + code + "&grant_type=authorization_code";
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
request.Method = "POST";
using (WebResponse response2 = request.GetResponse())
{
using (StreamReader reader = new StreamReader(response2.GetResponseStream(), Encoding.UTF8))
{
//得到url返回的数据
json = reader.ReadToEnd();
}
} //下面可以解析了
if (!string.IsNullOrEmpty(json))
{
//需要添加引用System.Web.Extensions
//然后还要添加using System.Web.Script.Serialization;
JavaScriptSerializer jss = new JavaScriptSerializer();
Dictionary<string, string> dic = jss.Deserialize<Dictionary<string, string>>(json);
string[] js = json.Replace("{", "").Replace("}", "").Split(‘,‘);
token = js[0].ToString().Split(‘:‘)[1].ToString().Substring(1, js[0].ToString().Split(‘:‘)[1].ToString().Length-2);
openid = js[3].ToString().Split(‘:‘)[1].ToString().Substring(1, js[3].ToString().Split(‘:‘)[1].ToString().Length-2);
}
}