.NET Community ToolkitでMVVMを試してみる（データバインディング）

<Window x:Class="WpfApp1.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:WpfMvvmToolkitApp1"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Window.DataContext>
        <local:NewMainViewModel/>
        <!--<local:OldMainViewModel/>-->
    </Window.DataContext>
    <StackPanel Margin="10">
        <TextBlock Text="姓："/>
        <TextBox Text="{Binding LastName}"/>
        <TextBlock Text="名："/>
        <TextBox Text="{Binding FirstName}"/>
        <TextBlock Text="氏名："/>
        <TextBlock Text="{Binding FullName}" Background="AliceBlue" />
    </StackPanel>
</Window>

using CommunityToolkit.Mvvm.ComponentModel;
using System.ComponentModel;

namespace WpfMvvmToolkitApp1;
public partial class NewMainViewModel : ObservableObject
{
    [ObservableProperty]
    [NotifyPropertyChangedFor(nameof(FullName))]
    private string firstName = "太郎";

    [ObservableProperty]
    [NotifyPropertyChangedFor(nameof(FullName))]
    private string lastName = "葡萄";

    public string FullName => $"{LastName} {FirstName}";
}

public partial class OldMainViewModel : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler? PropertyChanged;

    private string firstName = "太郎";
    public string FirstName
    {
        get => firstName;
        set
        {
            firstName = value;
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(FullName)));
        }
    }

    private string lastName = "葡萄";
    public string LastName
    {
        get => lastName;
        set
        {
            lastName = value;
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(FullName)));
        }
    }

    public string FullName => $"{LastName} {FirstName}";
}