Add project files.

Views/MainWindow.xaml

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+<Window x:Class="MVVM_DEMO.MainWindow"
+        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+        xmlns:local="clr-namespace:MVVM_DEMO"
+        xmlns:vm="clr-namespace:MVVM_DEMO.ViewModels"
+        mc:Ignorable="d"
+        Title="MainWindow"
+        Height="450"
+        Width="800">
+    <Window.DataContext>
+        <vm:MainViewModel />
+    </Window.DataContext>
+
+    <Grid>
+        <StackPanel>
+            <ComboBox x:Name="comboBox"
+                      Width="200"
+                      Height="30"
+                      Margin="10"
+                      VerticalAlignment="Top"
+                      ItemsSource="{Binding Products}"
+                      DisplayMemberPath="ProductName" />
+            <Button x:Name="btnAddProduct"
+                    Content="Add Product"
+                    Width="100px"
+                    Height="25px"
+                    Click="btnAddProduct_Click" />
+            <Label Content="Selected Product Details"
+                   FontWeight="Bold"
+                   FontSize="16"
+                   Margin="10" />
+            <TextBox x:Name="txtProductName"
+                     Width="200"
+                     Height="30"
+                     Text="{Binding productName}" 
+                     />
+            <TextBox x:Name="txtProductPrice"
+                     Width="200"
+                     Height="30"
+                     Text="{Binding productPrice}" />
+        </StackPanel>
+    </Grid>
+</Window>

Views/MainWindow.xaml.cs

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+using MVVM_DEMO.Models;
+using MVVM_DEMO.ViewModels;
+using System.Text;
+using System.Windows;
+using System.Windows.Controls;
+using System.Windows.Data;
+using System.Windows.Documents;
+using System.Windows.Input;
+using System.Windows.Media;
+using System.Windows.Media.Imaging;
+using System.Windows.Navigation;
+using System.Windows.Shapes;
+
+namespace MVVM_DEMO
+{
+    /// <summary>
+    /// Interaction logic for MainWindow.xaml
+    /// </summary>
+    public partial class MainWindow : Window
+    {
+        MainViewModel viewModel = new MainViewModel();
+
+        public MainWindow()
+        {
+            InitializeComponent();
+            this.DataContext = viewModel;
+            comboBox.SelectionChanged += ComboBox_SelectionChanged;
+            // initial selection
+            if (comboBox.Items.Count > 0)
+            {
+                comboBox.SelectedIndex = 0;
+            }
+        }
+
+        private void ComboBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
+        {
+            // display selected product details
+            if (comboBox.SelectedItem != null)
+            {
+                viewModel.productName= ((Product)comboBox.SelectedItem).ProductName;
+                viewModel.productPrice = (int)((Product)comboBox.SelectedItem).Price;
+                viewModel.OnPropertyChanged("productName");
+                viewModel.OnPropertyChanged("productPrice");
+            }
+
+        }
+
+        private void btnAddProduct_Click(object sender, RoutedEventArgs e)
+        {
+            // toevoegen van een product in het viewmodel
+            Product p = new Product();
+            p.ProductName = $"Product {viewModel.Products.Count + 1}";
+            // generate a random price between 10 and 100
+            Random rand = new Random();
+            p.Price = rand.Next(10, 100);
+            viewModel.Products.Add(p);
+        }
+    }
+}