public PrivateMessageList Copy()
        {
            var messageList = new PrivateMessageList();

            foreach (var message in MessageList)
            {
                messageList.AddMessage(message.Copy());
            }
            return(messageList);
        }
        public PrivateMessageList GetMessageById(string id)
        {
            var messageList = new PrivateMessageList();

            foreach (var message in MessageList)
            {
                if (message.SenderId == id || message.ReceiverId == id)
                {
                    messageList.AddMessage(message);
                }
            }
            return(messageList);
        }