Getting Started with Facebook Desktop (Client) Applications, C#, WPF / XAML and JSON

using System;
using System.Collections.Generic;

namespace Facebook
{
    /// <summary>
    /// Class containing all you need to login in and set up a session is in this class
    /// </summary>
    internal class Login
    {
        /// <summary>
        /// Create an Auth Token, login to facebook and set up a session for further API calls
        ///  http://wiki.developers.facebook.com/index.php/How_Facebook_Authenticates_Your_Application
        /// </summary>
        internal static Facebook.auth.getSession LoginAndGetSession()
        {
            string facebookAuthToken = CreateAuthToken(); // Step 1: Create Auth token
            LoginToFacebook(facebookAuthToken);           // Step 2: Login to facebook
            return GetSession(facebookAuthToken);         // Step 3: Return a session 
        }

        /// <summary>
        /// Create an Auth Token for facebook
        /// </summary>
        private static string CreateAuthToken()
        {
            // Create a token to use for the facebook session
            var parameters = new SortedDictionary<string, string>();  // Facebook parameter list (key value pair) that (needs to be sorted in order to get the MD5 hash correct - see Facebook.Security
            parameters.Add("method", "facebook.auth.createToken"); // http://wiki.developers.facebook.com/index.php/Auth.createToken
            string jsonResult = Facebook.Web.SendCallToFacebook(parameters);
            return JSON.Helper.StripSingleResult(jsonResult); // Return the Auth Token
        }

        /// <summary> 
        /// Login to facebook - needs to be done via the facebook web front end  
        /// </summary>
        private static void LoginToFacebook(string facebookAuthToken)
        {
            // Call the web form to do the facebook login - I couldnt find an easy work-around for a silent login :(
            var facebookLoginForm = new Facebook.Windows.Login(Facebook.Login.GetFacebookLoginPage(facebookAuthToken));
            facebookLoginForm.ShowDialog();
            if (!facebookLoginForm.AuthenticatedSuccessfully) throw new Exception("Error: facebook login failure");  // If not logged in, we can go no further
        }

        /// <summary>
        /// Create the facebook API session - http://wiki.developers.facebook.com/index.php/Auth.getSession
        /// </summary>
        private static Facebook.auth.getSession GetSession(string facebookAuthToken)
        {
            var parameters = new SortedDictionary<string, string>();  // Facebook parameter list (key value pair) that (needs to be sorted in order to get the MD5 hash correct - see Facebook.Security
            parameters.Add("method", "facebook.auth.getSession"); // http://wiki.developers.facebook.com/index.php/Auth.getSession
            parameters.Add("auth_token", facebookAuthToken);
            parameters.Add("generate_session_secret", "false");

            string jsonResult = Facebook.Web.SendCallToFacebook(parameters);
            return (JSON.Helper.Deserialize<Facebook.auth.getSession>(jsonResult));
        }

        /// <summary>
        /// Generate a url for login to facebook - this needs to be done against the facebook front end (for security reasons they say).
        /// </summary>
        /// <param name="auth_token"></param>
        /// <returns></returns>
        private static string GetFacebookLoginPage(string auth_token)
        {
            return String.Format(Facebook.Properties.Settings.Default.LoginUrl, Facebook.Properties.Settings.Default.ApplicationKey, auth_token, Facebook.Properties.Settings.Default.ApiVersion);
        }
    }
}