Adding Customers now works.

WD7UVN_SzTGUI_2023242.Client.WPF/ViewModels/CreateNewCustomerViewModel.cs

@@ -0,0 +1,56 @@
+using WD7UVN_HFT_2023241.Models;
+using System.ComponentModel;
+using System.Windows;
+using CommunityToolkit.Mvvm.ComponentModel;
+using System.Windows.Input;
+using CommunityToolkit.Mvvm.Input;
+using System;
+
+namespace WD7UVN_SzTGUI_2023242.Client.WPF.ViewModels
+{
+    public class CreateNewCustomerViewModel : ObservableRecipient
+    {
+        public Action CloseAction { get; set; }
+        public event Action<Customer> NewCustomerCreated;
+
+        public Customer newCustomer;
+        public Customer NewCustomer
+        {
+            get { return newCustomer; }
+            set
+            {
+                SetProperty(ref newCustomer, value);
+                (CreateCommand as RelayCommand).NotifyCanExecuteChanged();
+            }
+        }
+
+        public ICommand CreateCommand { get; set; }
+
+        public static bool IsInDesignMode
+        {
+            get
+            {
+                var prop = DesignerProperties.IsInDesignModeProperty;
+                return (bool)DependencyPropertyDescriptor.FromProperty(prop, typeof(FrameworkElement)).Metadata.DefaultValue;
+            }
+        }
+
+        public CreateNewCustomerViewModel()
+        {
+            newCustomer = new Customer();
+
+            if (!IsInDesignMode)
+            {
+                CreateCommand = new RelayCommand(() =>
+                {
+                    NewCustomerCreated?.Invoke(NewCustomer);
+                    CloseAction();
+                },
+                () =>
+                {
+                    return NewCustomer != null;
+                });
+            }
+        }
+    }
+}