Question

I am building a helper class that would allow me to manage facebook account in a windows form application. I am using Facebook C# SDK. As it is suggested in its documentation, to know if the user is authenticated one would get the loginUrl

       var loginUrl = oauth.GetLoginUrl(parameters);

and then afterward, navigate to that Url

webBrowser.Navigate(loginUrl);

Since I am on the back end of the application, I wonder how one can write a helper class that will return true or false to show if the user is authenticated or not. I would love to do something like:

public static  bool IsUserAunthenticated (string appId, string[] extendedPermissions)

How can this function be written? Any ideas? Remember I am using windows form on .net 4.0

Answer 1

assuming this function is called some time after

webBrowser.Navigate(loginURL)

A solution like this could work:

assuming:

• The user has already authorized your application

• ‘facebookClient’ is a static class field is already initialized

  public static bool isUserAuthenticated()  {
  try
  {
      facebookClient.Get("/me");
  
      //the lack of an exception thrown is a sign of success
      return true;
  }
  catch (FacebookOAuthException e)
  {
      //your access token used to initialize 'facebookClient' is invalid
      return false;
  } }
  

Some general notes:

• you didn’t show any code to handle the retrieval of the actual access
  token. I’ve been assuming you left that out for brevity.

• passing in ‘appID’ and ‘extendedPermissions’ means that this method
  would be used to REGISTER the user, not for testing to see if they
  were already a user of your application.

• related to the above point, you could pass in the access token as an
  argument so you would be able to initialize ‘facebookClient’ inside
  the method and run the authentication test.

To sum that last little bit up, if you’re not already aware, you need to realize there are two distinct stages: getting the access token and using the access token.