跳转到服务器报400错误，大家帮我看看有啥错误

Question

这是后台代码，前台没有任何操作。。。。。。

public partial class cb : System.Web.UI.Page
    {
        JavaScriptSerializer js = new JavaScriptSerializer();

        protected void Page_Load(object sender, EventArgs e)
        {
            string code = Request.QueryString["code"].ToString();
            if (!string.IsNullOrEmpty(code))
            {
                string appkey = ConfigurationManager.AppSettings["appkey"];
                string secret = ConfigurationManager.AppSettings["secret"];
                string redirect_uri = ConfigurationManager.AppSettings["redirect_uri"];

                //code = Request.QueryString["code"].ToString();

                WebUtils webUtils = new WebUtils();
                IDictionary<string, string> pout = new Dictionary<string, string>();
                pout.Add("grant_type", "authorization_code");
                pout.Add("client_id", appkey);
                pout.Add("client_secret", secret);
                pout.Add("code", code);
                pout.Add("redirect_uri", redirect_uri);
                // 沙箱
                string output = webUtils.DoPost("https://oauth.tbsandbox.com/token", pout);
                // 正式
                //string output = webUtils.DoPost("https://oauth.taobao.com/token", pout);

                cbModel cbmodel = js.Deserialize<cbModel>(output);
                // Access token
                string sessionKey = cbmodel.access_token;
                // Access token过期时间
                long expires_in = cbmodel.expires_in;

                Application["SessionKey"] = sessionKey;
                Application["ExpiresIn"] = expires_in;

            }
        }
    }

Answer 1

 webUtils.DoPost("https:  出错了。

Answer 2

配置问题。