微信网页获取openId

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

public class UserAuth : IHttpHandler
{
public void ProcessRequest(HttpContext context)
{

var appid = "wxf1c24c60e3ac13b7";
var secret = "5902b9817acb7a290d4b7c2e6e97d4d3";

var code = context.Request.QueryString["Code"];
if (string.IsNullOrEmpty(code))
{
var url = string.Format("https://open.weixin.qq.com/connect/oauth2/authorize?appid={0}&redirect_uri=http%3a%2f%2fwx.alinq.org%2fTest%2fUserAuth.ashx&response_type=code&scope=snsapi_userinfo&state=STATE#wechat_redirect", appid);
context.Response.Redirect(url);
}
else
{
var client = new System.Net.WebClient();
client.Encoding = System.Text.Encoding.UTF8;

var url = string.Format("https://api.weixin.qq.com/sns/oauth2/access_token?appid={0}&secret={1}&code={2}&grant_type=authorization_code", appid, secret, code);
var data = client.DownloadString(url);

var serializer = new JavaScriptSerializer();
var obj = serializer.Deserialize<Dictionary<string, string>>(data);
string accessToken;
if (!obj.TryGetValue("access_token", out accessToken))
return;

var opentid = obj["openid"];
url = string.Format("https://api.weixin.qq.com/sns/userinfo?access_token={0}&openid={1}&lang=zh_CN", accessToken, opentid);
data = client.DownloadString(url);
var userInfo = serializer.Deserialize<Dictionary<string, object>>(data);
foreach (var key in userInfo.Keys)
{
context.Response.Write(string.Format("{0}: {1}", key, userInfo[key]) + "<br/>");
}
}
}
}