Register with facebook

You should first go to https://developers.facebook.com/apps and register as a facebook developer.

1. Create a new App for the application.
2. Get the App ID assigned to you. for example: 124495023432023, and add to config.xml
   • <Facebook.App.Id>124495023432023</Facebook.App.Id>
3. In facebook Product Setup page, click "Get Started" for "Facebook Login".
4. Go to https://developers.facebook.com/apps/124495023432023/fb-login/settings/ (replace the id with yours)
5. Ensure only the following are enabled:
   • "Client OAuth Login"
   • Embedded Browser OAuth Login
6. Set Valid OAuth Redirect URLs to https://www.facebook.com/connect/login_success.html

Register with Facebook button

In the app if you want to read the user's details from facebook to allow simplier registration, you can then read the data using:

var user = await Facebook.Register(Facebook.Field.First_name, Facebook.Field.Last_name, Facebook.Field.Email, ...);
if (user != null)
{
      // Successful. Now you can use the data.
}

Log in with Facebook button

In the app if you want to allow logging in with facebook, then a secure approach is the following:

Button code:

var accessToken = await Facebook.Login(Facebook.Field.Email);
if (accessToken.HsaValue())
{
      // Successful. Now use the API to generate a login token.
      var sessionToken = await HttpPost<string>("v1/login/facebook/" + accessToken);
      Device.IO.File("SessionToken.txt").WriteAllText(sessionToken);     
}

API Code:

   [HttpPost, Route("login/facebook/{accessToken}")]
   public IHttpActionResult LoginWithFacebook(string accessToken)
   {
         var json = ("https://" + "graph.facebook.com/me?fields=email&access_token=" + accessToken).AsUri().Download();
         var email = JsonConvert.DeserializeObject<JObject>(json)?.Property("email")?.Value?.ToString();

         if (email.IsEmpty()) return BadRequest("Invalid email.");
         var member = Database.Find<Member>(m => m.Email == email);

         if (member == null) return BadRequest($"The email '{email}' is not registered in our system. Please register.");

         var result = JwtAuthentication.CreateTicket(member);
         return Ok(result);
   }