MVC 5 Owin Facebook的验证结果空引用异常 [英] MVC 5 Owin Facebook Auth results in Null Reference Exception

问题描述

我试图安装集成OWIN Facebook验证一个新的MVC项目5在Visual Studio 2013年我已经配置的应用程序和按键按照本教程：

I'm trying to setup integrated OWIN Facebook authentication in a new MVC 5 project in Visual Studio 2013. I have configured apps and keys as per this tutorial:

<一个href=\"http://www.asp.net/mvc/tutorials/mvc-5/create-an-aspnet-mvc-5-app-with-facebook-and-google-oauth2-and-openid-sign-on\">http://www.asp.net/mvc/tutorials/mvc-5/create-an-aspnet-mvc-5-app-with-facebook-and-google-oauth2-and-openid-sign-on

不过，我得到了的AccountController从这个函数抛出一个NullReferenceException：

However, I'm getting a NullReferenceException thrown from this call in the AccountController:

    [AllowAnonymous]
    public async Task<ActionResult> ExternalLoginCallback(string returnUrl)
    {
        var loginInfo = await AuthenticationManager.GetExternalLoginInfoAsync();

我已经检查了菲德勒的反应和我得到什么似乎是来自Facebook成功响应，但仍获得此错误。响应看起来是这样的：

I already checked the response in Fiddler and am getting what appears to be a success response from Facebook, but still get this error. The response looks like this:

{"id":"xxx","name":"xxx","first_name":"xxx","last_name":"xxx","link":
"https:\/\/www.facebook.com\/profile.php?id=xxx","location":{"id":"xxx","name":"xxx"},
"gender":"xxx","timezone":1,"locale":"en_GB","verified":true,"updated_time":"2013-10-23T10:42:23+0000"}

在HTTP调试时以及HTTPS我得到这个。我猜这是一个框架错误，但迄今绘制的空白，通过反射镜诊断这一点。

I get this when debugging in http as well as https. I'm guessing this is a framework bug but have so far drawn a blank diagnosing this through reflector.

推荐答案

这可能是身份OWIN扩展code的错误。我不能瑞普问题作为我的Facebook负载始终返回JSON用户名场，这是从你的FB回应失踪。我不明白为什么它不存在。

This probably is a bug in identity OWIN extension code. I can't repro the issue as my facebook payload always returns a username field in json, which is missing from your fb response. I am not quite sure why it's not there.

在身份owin扩展方法的code不具有标识的名称要求空支票是一样的用户名字段。我们已经提交了错误的它在内部。

The code in identity owin extension method doesn't have a null check for the identity's name claim which is same as the username field. We have filed a bug for it internally.

为了解决这个问题，你可以尝试用以下code免去您ExternalLoginCallback方式：

In order to workaround this issue, could you try replacing your ExternalLoginCallback method with following code:

   [AllowAnonymous]
    public async Task<ActionResult> ExternalLoginCallback(string returnUrl)
    {
        var result = await AuthenticationManager.AuthenticateAsync(DefaultAuthenticationTypes.ExternalCookie);
        if (result == null || result.Identity == null)
        {
            return RedirectToAction("Login");
        }

        var idClaim = result.Identity.FindFirst(ClaimTypes.NameIdentifier);
        if (idClaim == null)
        {
            return RedirectToAction("Login");
        }

        var login = new UserLoginInfo(idClaim.Issuer, idClaim.Value);
        var name = result.Identity.Name == null ? "" : result.Identity.Name.Replace(" ", "");

        // Sign in the user with this external login provider if the user already has a login
        var user = await UserManager.FindAsync(login);
        if (user != null)
        {
            await SignInAsync(user, isPersistent: false);
            return RedirectToLocal(returnUrl);
        }
        else
        {
            // If the user does not have an account, then prompt the user to create an account
            ViewBag.ReturnUrl = returnUrl;
            ViewBag.LoginProvider = login.LoginProvider;
            return View("ExternalLoginConfirmation", new ExternalLoginConfirmationViewModel { UserName = name });
        }
    }

在code将设置默认的用户名作为空当没有用户名来自Facebook /谷歌回来了。

The code will set default user name as empty when there is no username back from facebook/google.

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