c# - 在 asp net 中从 facebook 获取用户电子邮件

Question

我正在尝试从 Facebook 获取用户名和用户电子邮件。我阅读了很多关于这个主题的信息，这是我的最终代码，出于某种原因只能在我的 facebook 应用程序管理员帐户上使用:

public partial class Startup
{
    public void ConfigureAuth(IAppBuilder app)
    {

        /*Other external login options*/

         var FacebookOptions = new FacebookAuthenticationOptions()
                {
                    AppId = "My App Id",
                    AppSecret = "My App Secret",
                    SignInAsAuthenticationType = DefaultAuthenticationTypes.ExternalCookie,
                    BackchannelHttpHandler = new FacebookBackChannelHandler(),
                    UserInformationEndpoint = "https://graph.facebook.com/v2.7/me?fields=id,name,email"
                };


    }
}
public class FacebookBackChannelHandler : HttpClientHandler
{
    protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, System.Threading.CancellationToken cancellationToken)
    {
        if (!request.RequestUri.AbsolutePath.Contains("/oauth"))
        {
            request.RequestUri = new Uri(request.RequestUri.AbsoluteUri.Replace("?access_token", "&access_token"));
        }

        return await base.SendAsync(request, cancellationToken);
    }
}
public class AccountController : Controller
{
    public async Task<ActionResult> ExternalLoginCallback(string returnUrl)
    {
        var loginInfo = await AuthenticationManager.GetExternalLoginInfoAsync();
        /*my sign in code that works on my facebook app admin account*/
    }  
}    

在每个帐户上，我得到 loginInfo.Email 等于 null。

在developers.facebook.com我有:

当有人点击“使用 Facebook 登录”时，他会收到以下消息:

如果我点击“查看您提供的信息”，我会得到:

我错过了什么？为什么它不起作用？

Answer 1

终于找到答案了!只需将 Scope = { "email"} 添加到 FacebookOptions 即可解决问题!

我现在的代码:

public partial class Startup
{
    public void ConfigureAuth(IAppBuilder app)
    {

        /*Other external login options*/

         var FacebookOptions = new FacebookAuthenticationOptions()
                {
                    AppId = "My App Id",
                    AppSecret = "My App Secret",
                    SignInAsAuthenticationType = DefaultAuthenticationTypes.ExternalCookie,
                    BackchannelHttpHandler = new FacebookBackChannelHandler(),
                    Scope = { "email" },
                    UserInformationEndpoint = "https://graph.facebook.com/v2.7/me?fields=id,name,email"
                };
    }
}

其余代码保持不变。如果此问题返回，我只为案例添加了错误页面:

public class AccountController : Controller
{
    public async Task<ActionResult> ExternalLoginCallback(string returnUrl)
    {
        var loginInfo = await AuthenticationManager.GetExternalLoginInfoAsync();
        if(loginInfo.Email == null)
        {
             return RedirectToAction("FacebookError", "Account");
        }
        /*my sign in code*/
    }  
}