在預設 MVC5 應用程序中的帳戶關聯步驟中從外部提供商 Google 和 Facebook 獲取電子郵件

顯然，您可以通過將範圍添加到對FacebookAuthenticationOptions像中的 Facebook 提供程序來執行此操作Startup.Auth.cs：

<http://blogs.msdn.com/b/webdev/archive/2013/10/16/get-more-information-from-social-providers-used-in-the-vs-2013-project-templates.aspx>

List<string> scope = new List<string>() { "email" };
var x = new FacebookAuthenticationOptions();
x.Scope.Add("email");
...
app.UseFacebookAuthentication(x);

如何與 Google 提供商做同樣的事情？類/對像沒有x.Scope屬性！GoogleAuthenticationOptions

請在這篇文章的底部查看更新！

以下適用於我的Facebook：

StartupAuth.cs：

var facebookAuthenticationOptions = new FacebookAuthenticationOptions()
{
   AppId = "x",
   AppSecret = "y"
};
facebookAuthenticationOptions.Scope.Add("email");
app.UseFacebookAuthentication(facebookAuthenticationOptions);

ExternalLoginCallback 方法：

var externalIdentity = HttpContext.GetOwinContext().Authentication.GetExternalIdentityAsync(DefaultAuthenticationTypes.ExternalCookie);
var emailClaim = externalIdentity.Result.Claims.FirstOrDefault(c => c.Type == ClaimTypes.Email);
var email = emailClaim.Value;

對於Google：

啟動驗證.cs

app.UseGoogleAuthentication();

ExternalLoginCallback 方法（與 facebook 相同）：

var externalIdentity = HttpContext.GetOwinContext().Authentication.GetExternalIdentityAsync(DefaultAuthenticationTypes.ExternalCookie);
var emailClaim = externalIdentity.Result.Claims.FirstOrDefault(c => c.Type == ClaimTypes.Email);
var email = emailClaim.Value;

如果我在這裡設置斷點：

var email = emailClaim.Value;

我在調試器中看到了 Facebook 和 Google 的電子郵件地址。

更新 1：舊的答案讓我感到困惑，所以我用我自己的項目中的程式碼更新了它，我剛剛調試過並且我知道它可以工作。

更新 2：使用新的ASP.NET Identity 2.0 RTM版本，您不再需要本文中的任何程式碼。獲取電子郵件的正確方法是簡單地執行以下操作：

1. 啟動.Auth.cs

   app.UseFacebookAuthentication(
      appId: "x",
      appSecret: "y");

   app.UseGoogleAuthentication();

2. AccountController.cs

//
// GET: /Account/ExternalLoginCallback
[AllowAnonymous]
public async Task<ActionResult> ExternalLoginCallback(string returnUrl)
{
   var loginInfo = await AuthenticationManager.GetExternalLoginInfoAsync();
   if (loginInfo == null)
   {
       return RedirectToAction("Login");
   }

   // Sign in the user with this external login provider if the user already has a login
   var result = await SignInHelper.ExternalSignIn(loginInfo, isPersistent: false);
   switch (result)
   {
       case SignInStatus.Success:
           return RedirectToLocal(returnUrl);
       case SignInStatus.LockedOut:
           return View("Lockout");
       case SignInStatus.RequiresTwoFactorAuthentication:
           return RedirectToAction("SendCode", new { ReturnUrl = returnUrl });
       case SignInStatus.Failure:
       default:
           // If the user does not have an account, then prompt the user to create an account
           ViewBag.ReturnUrl = returnUrl;
           ViewBag.LoginProvider = loginInfo.Login.LoginProvider;
           return View("ExternalLoginConfirmation", new ExternalLoginConfirmationViewModel { Email = loginInfo.Email });
   }
}

引用自：https://stackoverflow.com/questions/20378043