应设置值时，HttpContext.Current.Session["accesstoken"].ToString() 为 null

Question

我在 Session["accesstoken"] 中设置从 facebook 检索到的 accesstoken。当我尝试检索它时，我被 nullreferenceexception 击中。

为什么？

在我开始使用 AddAdditionalPermissions 方法之前它确实有效，但我看不出这会如何干扰 Session...？

在调试模式下，我从 result.ExtraData["accesstoken"] 复制了值，并通过 formscollection 将其添加到代码中（如您在 Facebook.cs 中所见），并且令牌有效。我应该改用 cookie 吗？

AccountController.cs

    public ActionResult ExternalLoginCallback(string returnUrl)
    {
        AuthenticationResult result =   
        OAuthWebSecurity.VerifyAuthentication(
                Url.Action("ExternalLoginCallback",
                new { ReturnUrl = returnUrl }));
        if (!result.IsSuccessful)
        {
            return RedirectToAction("ExternalLoginFailure");
        }

        // Save the accesstoken into session
        Session["accesstoken"] = result.ExtraData["accesstoken"];
        Session["id"] = result.ExtraData["id"];

        if (OAuthWebSecurity.Login(result.Provider, result.ProviderUserId, createPersistentCookie: false))
        {
            AddAdditionalPermissions();
            return RedirectToLocal(returnUrl);
        }(...etcetera) 

附加权限功能：

private void AddAdditionalPermissions() { 字符串 facebook_urlAuthorize_base = "https://graph.facebook.com/oauth/authorize"; 字符串 facebook_urlGetToken_base = "https://graph.facebook.com/oauth/access_token"; 字符串 facebook_AppID = "1secretappIdhere242341"; string facebook_AppSecret = "1secretcodeheteq4426";

        string scope = "publish_stream"; 
        string urlAuthorize = facebook_urlAuthorize_base;
        urlAuthorize += "?client_id=" + facebook_AppID;
        urlAuthorize += "&redirect_uri=" + "http://localhost:2730/";
        urlAuthorize += "&scope=" + scope;

        Response.Redirect(urlAuthorize, true);             
    }

Facebook.cs

public void PostToFacebook(FormCollection fm) { var fb = new FacebookClient();

        fb = new FacebookClient(HttpContext.Current.Session["accesstoken"].ToString());
        var args = new Dictionary<string, object>();
        args["message"] = "abc";

        fb.Post("/me/feed", args);
    }

Answer 1

我认为您的会话令牌 cookie 丢失了。通过替换

尝试不终止当前页面响应

Response.Redirect(urlAuthorize, true);       

与

Response.Redirect(urlAuthorize, false);     

看看有没有帮助。