/// <summary>
        /// This Deletes the Customer from the List and deactivates thew Customer, but the Customer is still in the Database.
        /// </summary>
        public void DeleteCustomer()
        {
            GlobalConfig.Connection.DeleteCustomer(SelectedCustomer);
            AvailableCustomers.Remove(SelectedCustomer);

            NotifyOfPropertyChange(() => AvailableCustomers);
        }
        /// <summary>
        /// gets a Model from CreateNewCustomer and Adds this Model to the List in the ManageCustomerView
        /// and also Add the Customer to the Database
        /// </summary>
        /// <param name="customerModel">
        /// This Param is a CustomerModel with all it needs to be saved in the Database
        /// </param>
        public void Handle(CustomerModel customerModel)
        {
            if (customerModel.FirstName == null)
            {
                LoadCreateCustomerIsVisible  = false;
                LoadCustomerDetailsIsVisible = false;
                CustomerListIsVisible        = true;
                SelectedCustomer             = null;
                return;
            }

            if (!AvailableCustomers.Any(c => customerModel.Id == c.Id))
            {
                AvailableCustomers.Add(customerModel);
            }

            LoadCreateCustomerIsVisible  = false;
            LoadCustomerDetailsIsVisible = false;
            CustomerListIsVisible        = true;
            SelectedCustomer             = null;
            AvailableCustomers           = new BindableCollection <CustomerModel>(GlobalConfig.Connection.Get_CustomerAll());
            ActiveCustomer(AvailableCustomers);
            NotifyOfPropertyChange(() => AvailableCustomers);
        }