/// <summary>
        /// adds a new customer
        /// </summary>
        public void AddMethod()
        {
            addWin = new AddUpdateWindow();
            Message addCust = new Message();

            addCust.isAdd = true;
            Messenger.Default.Send(addCust);
            addWin.Show();
            Messenger.Default.Register <NotificationMessage>(this, (msg) => {
                if (msg.Notification == "Close")
                {
                    addWin.Close();
                    Messenger.Default.Register <Customer>(this, finish);
                }
            });
        }
        /// <summary>
        /// modifies a customer
        /// </summary>
        public void ModMethod()
        {
            modWin = new AddUpdateWindow();
            Message modCust = new Message();

            modCust.isAdd = false;
            //modCust.id = selectedCustomer.CustomerID;
            modCust.c = selectedCustomer;
            Messenger.Default.Send(modCust);
            modWin.Show();
            Messenger.Default.Register <NotificationMessage>(this, (msg) => {
                if (msg.Notification == "Close")
                {
                    modWin.Close();
                    Messenger.Default.Register <Customer>(this, finish);
                }
            });
        }