1，在config.json文件中添加AzureAD的配置信息：

"AzureAd": {
  "ClientId": "[Enter the clientId of your application as obtained from portal, e.g. ba74781c2-53c2-442a-97c2-3d60re42f403]",
  "Tenant": "[Enter the name of your tenant, e.g. contoso.onmicrosoft.com]",
  "AadInstance": "https://login.microsoftonline.com/{0}", // This is the public instance of Azure AD
  "PostLogoutRedirectUri": https://localhost:44322/
}

2，修改project.json，引入OpenIdConnect的中间件：

"Microsoft.AspNet.Authentication.OpenIdConnect": "1.0.0-*"

3，在Startup中的ConfigureServices方法里面添加：

// OpenID Connect Authentication Requires Cookie Auth
services.Configure(options =>
{
  options.SignInScheme = CookieAuthenticationDefaults.AuthenticationScheme;
});

4，在Startup中的Configure方法里面添加：

// Configure the OWIN Pipeline to use Cookie Authentication
app.UseCookieAuthentication(options => 
{
  // By default, all middleware are passive/not automatic. Making cookie middleware automatic so that it acts on all the messages.
  options.AutomaticAuthentication = true;

});

// Configure the OWIN Pipeline to use OpenId Connect Authentication
app.UseOpenIdConnectAuthentication(options =>
{
  options.ClientId = Configuration.Get("AzureAd:ClientId");
  options.Authority = String.Format(Configuration.Get("AzureAd:AadInstance"), Configuration.Get("AzureAd:Tenant"));
  options.PostLogoutRedirectUri = Configuration.Get("AzureAd:PostLogoutRedirectUri");
  options.Notifications = new OpenIdConnectAuthenticationNotifications
  {
    AuthenticationFailed = OnAuthenticationFailed,
  };
});

5，Startup的OnAuthenticationFailed方法为：

private Task OnAuthenticationFailed(AuthenticationFailedNotification notification)
{
  notification.HandleResponse();
  notification.Response.Redirect("/Home/Error?message=" + notification.Exception.Message);
  return Task.FromResult(0);
}

6，添加一个名为AccountController的Controller：

public class AccountController : Controller
{
  // GET: /Account/Login
  [HttpGet]
  public IActionResult Login()
  {
    if (Context.User == null || !Context.User.Identity.IsAuthenticated)
      return new ChallengeResult(OpenIdConnectAuthenticationDefaults.AuthenticationScheme, new AuthenticationProperties { RedirectUri = "/" });
    return RedirectToAction("Index", "Home");
  }

  // GET: /Account/LogOff
  [HttpGet]
  public IActionResult LogOff()
  {
    if (Context.User.Identity.IsAuthenticated)
    {
      Context.Authentication.SignOut(CookieAuthenticationDefaults.AuthenticationScheme);
      Context.Authentication.SignOut(OpenIdConnectAuthenticationDefaults.AuthenticationScheme);
    }
    return RedirectToAction("Index", "Home");
  }
}

如果你遇到添加了 [Authorize] ，但是不能自动转到登录页面的情况，那么需要：

app.UseOpenIdConnectAuthentication(options => {
  options.AutomaticAuthentication = true;
});