如何使用 ASP.Net Core Identity 从登录用户处检索 Facebook 个人资料图片？

Question

我有一个可行的解决方案，但我想知道这是否是正确的方法。这是我到目前为止所得到的。

我将 ASP.Net Core 1.1.2 与 ASP.NET Core Identity 1.1.2 一起使用。

Startup.cs 中的重要部分如下所示：

    public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
    {
        //...
        app.UseFacebookAuthentication(new FacebookOptions
        {
            AuthenticationScheme = "Facebook",
            AppId = Configuration["ExternalLoginProviders:Facebook:AppId"],
            AppSecret = Configuration["ExternalLoginProviders:Facebook:AppSecret"]
        });
    }

FacebookOptions 附带 Microsoft.AspNetCore.Authentication.Facebook nuget 包。

AccountController.cs 中的回调函数如下所示：

    [HttpGet]
    [AllowAnonymous]
    public async Task<IActionResult> ExternalLoginCallback(string returnUrl = null, string remoteError = null)
    {
        //... SignInManager<User> _signInManager; declared before
        ExternalLoginInfo info = await _signInManager.GetExternalLoginInfoAsync();
        SignInResult signInResult = await _signInManager.ExternalLoginSignInAsync(info.LoginProvider, info.ProviderKey, isPersistent: false);

        byte[] thumbnailBytes = null;

        if (info.LoginProvider == "Facebook")
        {
            string nameIdentifier = info.Principal.FindFirstValue(ClaimTypes.NameIdentifier);
            string thumbnailUrl = $"https://graph.facebook.com/{nameIdentifier}/picture?type=large";
            using (HttpClient httpClient = new HttpClient())
            {
                thumbnailBytes = await httpClient.GetByteArrayAsync(thumbnailUrl);
            }
        }
        //...
    }

所以这段代码工作得很好，但是，如前所述，这是正确的方法（从技术上讲，不是基于意见）吗？

Answer 1

要从 Facebook 获取个人资料图片，您需要配置 Facebook 选项并从 OAuth 订阅 OnCreatingTicket 事件。

services.AddAuthentication().AddFacebook("Facebook", options =>
{

    options.SignInScheme = IdentityServerConstants.ExternalCookieAuthenticationScheme;
    options.ClientId = configuration.GetSection("ExternalLogin").GetSection("Facebook").GetSection("ClientId").Value;
    options.ClientSecret = configuration.GetSection("ExternalLogin").GetSection("Facebook").GetSection("ClientSecret").Value;
    options.Fields.Add("picture");
    options.Events = new OAuthEvents
    {
        OnCreatingTicket = context =>
        {
            var identity = (ClaimsIdentity)context.Principal.Identity;
            var profileImg = context.User["picture"]["data"].Value<string>("url");
            identity.AddClaim(new Claim(JwtClaimTypes.Picture, profileImg));
            return Task.CompletedTask;
        }
    };
});