public void Broadcast(string to, Colleague fromColleague, string message)
        {
            Colleague colleague;

            if (to == "All")
            {
                foreach (Colleague c in _colleagues.Values)
                {
                    c.Receive(fromColleague.Name, message);
                }
            }
            else if (_colleagues.ContainsKey(to))
            {
                _colleagues.TryGetValue(to, out colleague);
                colleague.Receive(fromColleague.Name, message);
            }
        }
 public void Register(Colleague colleague)
 {
     _colleagues.Add(colleague.Name, colleague);
 }