AgFx pattern to verify you have valid data (either from cache or web)

gistfile1.cs

public void AuthenticateUser(Action<AuthorizedUser> completed, Action<Exception> error)
{
    EnsureIsAuthenticated();

    AuthorizedUser = DataManager.Current.LoadFromCache<AuthorizedUser>("authenticated_user");

    // LoadFromCache returns an object even if it didn't exist in the
    // cache so check one of its properties for existance vs. the object
    // itself.
    if (!String.IsNullOrEmpty(AuthorizedUser.Id))
    {
        if (completed != null)
            completed(AuthorizedUser);
        return;
    }

    // Force a network request of the AuthorizedUser because the code
    // above has just confirmed it doesn't exist in the cache.  This
    // funky deconstruction of what a normal Load<>() does is so the
    // calling code can wait on getting a "real" instance vs. an
    // empty one that then pops with live data.
    DataManager.Current.Refresh<AuthorizedUser>(
        "authenticated_user",
        user =>
        {
            this.AuthorizedUser = user;
            if (completed != null)
                completed(AuthorizedUser);
        },
        e =>
        {
            if (error != null)
            {
                error(e);
            }                    
        });
}