// public Command SendCommand { get; }
        // public UserMessage UM { get; set; }
        public MessageViewModel(UserDetailData recip, string senderId)
        {
            Recip    = recip;
            Title    = Recip.FirstName + " " + Recip.LastName;
            SenderId = senderId;
            Messages = new ObservableCollection <UserMessage>();

            LoadMessagesCommand = new Command(async() => await ExecuteLoadMessages());
            //SendCommand = new Command(Send);
            MessagingCenter.Subscribe <MessagePage, UserMessage>(this, "SendMessage", async(obj, message) =>
            {
                var newMessage = message as UserMessage;
                await MessageStore.AddMessageAsync(newMessage);
                Messages.Add(newMessage);
            });
        }