void OnCustomerAddedToRepository(object sender, CustomerAddedEventArgs e)
 {
     var viewModel = new CustomerViewModel(e.NewCustomer, _customerRepository);
     this.AllCustomers.Add(viewModel);
 }
        void OnCustomerAddedToRepository(object sender, CustomerAddedEventArgs e)
        {
            var viewModel = new CustomerViewModel(e.NewCustomer, _customerRepository);

            this.AllCustomers.Add(viewModel);
        }