WPF vs WinForms vs WinUI vs Avalonia vs MAUI: one ViewModel under WinForms, WPF and Avalonia on net10.0

dotnet-platform-specific/DesktopUiFrameworks/Converter.Avalonia/App.axaml

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+<Application xmlns="https://github.com/avaloniaui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             x:Class="Converter.Avalonia.App"
+             RequestedThemeVariant="Default">
+    <Application.Styles>
+        <FluentTheme />
+    </Application.Styles>
+</Application>

dotnet-platform-specific/DesktopUiFrameworks/Converter.Avalonia/App.axaml.cs

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+using Avalonia;
+using Avalonia.Controls.ApplicationLifetimes;
+using Avalonia.Markup.Xaml;
+
+namespace Converter.Avalonia;
+
+public partial class App : Application
+{
+    public override void Initialize() => AvaloniaXamlLoader.Load(this);
+
+    public override void OnFrameworkInitializationCompleted()
+    {
+        if (ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
+        {
+            desktop.MainWindow = new MainWindow();
+        }
+
+        base.OnFrameworkInitializationCompleted();
+    }
+}

dotnet-platform-specific/DesktopUiFrameworks/Converter.Avalonia/Converter.Avalonia.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>WinExe</OutputType>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Avalonia" Version="12.1.3" />
+    <PackageReference Include="Avalonia.Desktop" Version="12.1.3" />
+    <PackageReference Include="Avalonia.Themes.Fluent" Version="12.1.3" />
+    <PackageReference Include="Avalonia.Fonts.Inter" Version="12.1.3" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Converter.Core\Converter.Core.csproj" />
+  </ItemGroup>
+
+</Project>

dotnet-platform-specific/DesktopUiFrameworks/Converter.Avalonia/MainWindow.axaml

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+<Window xmlns="https://github.com/avaloniaui"
+        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+        xmlns:core="using:Converter.Core"
+        x:Class="Converter.Avalonia.MainWindow"
+        x:DataType="core:ConverterViewModel"
+        Title="Converter (Avalonia)" Width="320" SizeToContent="Height">
+    <Window.DataContext>
+        <core:ConverterViewModel />
+    </Window.DataContext>
+    <StackPanel Margin="12">
+        <TextBox Text="{Binding Celsius}" />
+        <Button Content="Convert" Command="{Binding ConvertCommand}" Margin="0,8" />
+        <TextBlock Text="{Binding Result}" />
+    </StackPanel>
+</Window>

dotnet-platform-specific/DesktopUiFrameworks/Converter.Avalonia/MainWindow.axaml.cs

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+using Avalonia.Controls;
+
+namespace Converter.Avalonia;
+
+public partial class MainWindow : Window
+{
+    public MainWindow() => InitializeComponent();
+}

dotnet-platform-specific/DesktopUiFrameworks/Converter.Avalonia/Program.cs

@@ -0,0 +1,15 @@
+using Avalonia;
+
+namespace Converter.Avalonia;
+
+internal static class Program
+{
+    [STAThread]
+    public static void Main(string[] args) =>
+        BuildAvaloniaApp().StartWithClassicDesktopLifetime(args);
+
+    public static AppBuilder BuildAvaloniaApp() =>
+        AppBuilder.Configure<App>()
+            .UsePlatformDetect()
+            .WithInterFont();
+}

dotnet-platform-specific/DesktopUiFrameworks/Converter.Core/Converter.Core.csproj

@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

dotnet-platform-specific/DesktopUiFrameworks/Converter.Core/ConverterViewModel.cs

@@ -0,0 +1,48 @@
+using System.ComponentModel;
+using System.Runtime.CompilerServices;
+
+namespace Converter.Core;
+
+public sealed class ConverterViewModel : INotifyPropertyChanged
+{
+    public ConverterViewModel() => ConvertCommand = new RelayCommand(Convert, CanConvert);
+
+    public event PropertyChangedEventHandler? PropertyChanged;
+
+    public RelayCommand ConvertCommand { get; }
+
+    public string Celsius
+    {
+        get;
+        set
+        {
+            if (field == value) return;
+            field = value;
+            OnPropertyChanged();
+            ConvertCommand.RaiseCanExecuteChanged();
+        }
+    } = "";
+
+    public string Result
+    {
+        get;
+        private set
+        {
+            field = value;
+            OnPropertyChanged();
+        }
+    } = "";
+
+    private bool CanConvert() => double.TryParse(Celsius, out _);
+
+    private void Convert()
+    {
+        if (double.TryParse(Celsius, out var celsius))
+        {
+            Result = $"{celsius * 9 / 5 + 32:0.#} °F";
+        }
+    }
+
+    private void OnPropertyChanged([CallerMemberName] string? name = null) =>
+        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
+}

dotnet-platform-specific/DesktopUiFrameworks/Converter.Core/RelayCommand.cs

@@ -0,0 +1,14 @@
+using System.Windows.Input;
+
+namespace Converter.Core;
+
+public sealed class RelayCommand(Action execute, Func<bool> canExecute) : ICommand
+{
+    public event EventHandler? CanExecuteChanged;
+
+    public bool CanExecute(object? parameter) => canExecute();
+
+    public void Execute(object? parameter) => execute();
+
+    public void RaiseCanExecuteChanged() => CanExecuteChanged?.Invoke(this, EventArgs.Empty);
+}

dotnet-platform-specific/DesktopUiFrameworks/Converter.Tests/AvaloniaWindowTests.cs

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+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Headless;
+using Avalonia.Input;
+using Converter.Avalonia;
+
+[assembly: AvaloniaTestApplication(typeof(App))]
+
+namespace Converter.Tests;
+
+public class AvaloniaWindowTests
+{
+    [Fact]
+    public async Task TypingAndClickingConvert_ShowsFahrenheit()
+    {
+        var session = HeadlessUnitTestSession.GetOrStartForAssembly(typeof(AvaloniaWindowTests).Assembly);
+
+        var (enabledBefore, enabledAfterTyping, result) = await session.Dispatch(() =>
+        {
+            var window = new MainWindow();
+            window.Show();
+            var panel = (StackPanel)window.Content!;
+            var celsiusBox = (TextBox)panel.Children[0];
+            var convertButton = (Button)panel.Children[1];
+            var resultText = (TextBlock)panel.Children[2];
+
+            var before = convertButton.IsEffectivelyEnabled;
+            celsiusBox.Focus();
+            window.KeyTextInput("100");
+            var afterTyping = convertButton.IsEffectivelyEnabled;
+
+            var center = convertButton.TranslatePoint(
+                new Point(convertButton.Bounds.Width / 2, convertButton.Bounds.Height / 2), window)!.Value;
+            window.MouseDown(center, MouseButton.Left);
+            window.MouseUp(center, MouseButton.Left);
+
+            return (before, afterTyping, resultText.Text);
+        }, TestContext.Current.CancellationToken);
+
+        Assert.False(enabledBefore);
+        Assert.True(enabledAfterTyping);
+        Assert.Equal("212 °F", result);
+    }
+}

dotnet-platform-specific/DesktopUiFrameworks/Converter.Tests/Converter.Tests.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <OutputType>Exe</OutputType>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Using Include="Xunit" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.10.1" />
+    <PackageReference Include="xunit.v3.mtp-off" Version="4.0.1" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="4.0.0" />
+    <PackageReference Include="Avalonia.Headless" Version="12.1.3" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Converter.Core\Converter.Core.csproj" />
+    <ProjectReference Include="..\Converter.Avalonia\Converter.Avalonia.csproj" />
+  </ItemGroup>
+
+</Project>

dotnet-platform-specific/DesktopUiFrameworks/Converter.Tests/ConverterViewModelTests.cs

@@ -0,0 +1,46 @@
+using Converter.Core;
+
+namespace Converter.Tests;
+
+public class ConverterViewModelTests
+{
+    [Fact]
+    public void ConvertCommand_IsDisabled_UntilCelsiusParses()
+    {
+        var viewModel = new ConverterViewModel();
+        Assert.False(viewModel.ConvertCommand.CanExecute(null));
+
+        viewModel.Celsius = "warm";
+        Assert.False(viewModel.ConvertCommand.CanExecute(null));
+
+        viewModel.Celsius = "100";
+        Assert.True(viewModel.ConvertCommand.CanExecute(null));
+    }
+
+    [Theory]
+    [InlineData("100", "212 °F")]
+    [InlineData("0", "32 °F")]
+    public void ConvertCommand_WritesFahrenheitToResult(string celsius, string expected)
+    {
+        var viewModel = new ConverterViewModel { Celsius = celsius };
+
+        viewModel.ConvertCommand.Execute(null);
+
+        Assert.Equal(expected, viewModel.Result);
+    }
+
+    [Fact]
+    public void SettingCelsius_NotifiesTheView()
+    {
+        var viewModel = new ConverterViewModel();
+        var changedProperties = new List<string?>();
+        var canExecuteChanges = 0;
+        viewModel.PropertyChanged += (_, e) => changedProperties.Add(e.PropertyName);
+        viewModel.ConvertCommand.CanExecuteChanged += (_, _) => canExecuteChanges++;
+
+        viewModel.Celsius = "25";
+
+        Assert.Equal([nameof(ConverterViewModel.Celsius)], changedProperties);
+        Assert.Equal(1, canExecuteChanges);
+    }
+}

dotnet-platform-specific/DesktopUiFrameworks/Converter.WinForms/BoundForm.cs

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+using Converter.Core;
+
+namespace Converter.WinForms;
+
+public sealed class BoundForm : Form
+{
+    public BoundForm(ConverterViewModel viewModel)
+    {
+        Text = "Converter (WinForms, bound)";
+
+        var celsiusBox = new TextBox { Width = 200 };
+        celsiusBox.DataBindings.Add(nameof(TextBox.Text), viewModel,
+            nameof(ConverterViewModel.Celsius), false, DataSourceUpdateMode.OnPropertyChanged);
+
+        var convertButton = new Button { Text = "Convert", Command = viewModel.ConvertCommand };
+
+        var resultLabel = new Label { AutoSize = true };
+        resultLabel.DataBindings.Add(nameof(Label.Text), viewModel, nameof(ConverterViewModel.Result));
+
+        Controls.Add(new FlowLayoutPanel
+        {
+            Dock = DockStyle.Fill,
+            FlowDirection = FlowDirection.TopDown,
+            Controls = { celsiusBox, convertButton, resultLabel }
+        });
+    }
+}

dotnet-platform-specific/DesktopUiFrameworks/Converter.WinForms/ClassicForm.cs

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+namespace Converter.WinForms;
+
+public sealed class ClassicForm : Form
+{
+    private readonly TextBox _celsiusBox = new() { Width = 200 };
+    private readonly Button _convertButton = new() { Text = "Convert", Enabled = false };
+    private readonly Label _resultLabel = new() { AutoSize = true };
+
+    public ClassicForm()
+    {
+        Text = "Converter (WinForms, classic)";
+        Controls.Add(new FlowLayoutPanel
+        {
+            Dock = DockStyle.Fill,
+            FlowDirection = FlowDirection.TopDown,
+            Controls = { _celsiusBox, _convertButton, _resultLabel }
+        });
+
+        _celsiusBox.TextChanged += (_, _) =>
+            _convertButton.Enabled = double.TryParse(_celsiusBox.Text, out _);
+
+        _convertButton.Click += (_, _) =>
+        {
+            var celsius = double.Parse(_celsiusBox.Text);
+            _resultLabel.Text = $"{celsius * 9 / 5 + 32:0.#} °F";
+        };
+    }
+}

dotnet-platform-specific/DesktopUiFrameworks/Converter.WinForms/Converter.WinForms.csproj

@@ -0,0 +1,16 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>WinExe</OutputType>
+    <TargetFramework>net10.0-windows</TargetFramework>
+    <UseWindowsForms>true</UseWindowsForms>
+    <EnableWindowsTargeting>true</EnableWindowsTargeting>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Converter.Core\Converter.Core.csproj" />
+  </ItemGroup>
+
+</Project>

dotnet-platform-specific/DesktopUiFrameworks/Converter.WinForms/Program.cs

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+using Converter.Core;
+
+namespace Converter.WinForms;
+
+internal static class Program
+{
+    [STAThread]
+    private static void Main(string[] args)
+    {
+        ApplicationConfiguration.Initialize();
+        Application.SetColorMode(SystemColorMode.System);
+
+        Form form = args.Contains("--classic")
+            ? new ClassicForm()
+            : new BoundForm(new ConverterViewModel());
+
+        Application.Run(form);
+    }
+}

dotnet-platform-specific/DesktopUiFrameworks/Converter.Wpf/App.xaml

@@ -0,0 +1,6 @@
+<Application x:Class="Converter.Wpf.App"
+             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             StartupUri="MainWindow.xaml"
+             ThemeMode="System">
+</Application>

dotnet-platform-specific/DesktopUiFrameworks/Converter.Wpf/App.xaml.cs

@@ -0,0 +1,7 @@
+using System.Windows;
+
+namespace Converter.Wpf;
+
+public partial class App : Application
+{
+}