如何从Azure Active Directory检索用户信息

我对Xamarin和Azure Active Directory有点陌生，所以请原谅我。我在试图从Azure Active Directory检索用户信息(名、姓和图片)时遇到麻烦。请注意，Azure Active Directory中的电子邮件是Google帐户。

每次我试图检索它，我只得到一个错误，它要求我再次验证只是为了检索我想要的。下面是我的代码:

 // Use MobileServices Login to authenticate user
 private async Task<bool> AuthenticateUsingMobileServices(Activity activity)
 {
      var success = false;
      try
      {
           // Sign in with Active Directory
           MobileUser = await MobileService.LoginAsync(activity, 
                MobileServiceAuthenticationProvider.WindowsAzureActiveDirectory);
           System.Diagnostics.Debug.WriteLine("you are now logged in - Logged in!");
           System.Diagnostics.Debug.WriteLine([insert user name here]);
           success = true;
      }
      catch (Exception ex)
      {
           System.Diagnostics.Debug.WriteLine("Authentication failed " + ex.ToString());
      }
}

我已经尝试添加这个除了我已经定义的ResourceUri和ClientId:

 AuthenticationContext authContext = new AuthenticationContext(CommonAuthority);
 AuthResult = await authContext.AcquireTokenAsync(ResourceUri, ClientId, UserCredential);

但是我不知道应该为ClientAssertion或UserAssertion放什么