private IList<long> GetAppUsers(bool isAsync, GetAppUsersCallback callback, Object state)
        {
            var parameterList = new Dictionary<string, string> {{"method", "facebook.friends.getAppUsers"}};

             if(isAsync)
            {
                SendRequestAsync<friends_getAppUsers_response, IList<long>>(parameterList, new FacebookCallCompleted<IList<long>>(callback), state, "uid");
                return null;
            }

             var response = SendRequest<friends_getAppUsers_response>(parameterList);
             return response == null ? null : response.uid;
        }
 /// <summary>
 /// Returns the identifiers for the current user's Facebook friends who have authorized the specific calling application.
 /// </summary>
 /// <example>
 /// <code>
 /// private static void RunDemoAsync()
 /// {
 ///     Api api = new Api(new DesktopSession(Constants.ApplicationKey, Constants.ApplicationSecret, Constants.SessionSecret, Constants.SessionKey));
 ///     api.Friends.GetAppUsersAsync(AsyncDemoCompleted, null);
 /// }
 ///
 /// private static void AsyncDemoCompleted(IList&lt;long&gt; result, Object state, FacebookException e)
 /// {
 ///     var actual = result;
 /// }
 /// </code>
 /// </example>
 /// <param name="callback">The AsyncCallback delegate</param>
 /// <param name="state">An object containing state information for this asynchronous request</param>        
 /// <returns>The friend IDs returned are those friends who have authorized the calling application, which is a subset of the friends returned from the friends.get method. If no friends are found, the method returns an empty friends_getAppUsers_response element.</returns>
 /// <remarks>The first array specifies one half of each pair, the second array the other half; therefore, they must be of equal size.</remarks>
 public void GetAppUsersAsync(GetAppUsersCallback callback, Object state)
 {
     GetAppUsers(true, callback, state);
 }