[MVVM] `AttachedProperty`/`DirectProperty`/`StyledProperty` source generators

[ero-qt]

Overview

Examples like these require a considerable amount of repetitive code:

public bool Foo
{
  get => GetValue(FooProperty);
  set => SetValue(FooProperty, value);
}

public ObservableCollection<BarViewModel>? BarsSource
{
  get => GetValue(BarsSourceProperty);
  set => SetValue(BarsSourceProperty, value);
}

public ICommand? BazCommand
{
  get => GetValue(BazCommandProperty);
  set => SetValue(BazCommandProperty, value);
}

public static readonly StyledProperty<bool> FooProperty =
  AvaloniaProperty.Register<QuxControl, bool>(nameof(Foo));

public static readonly StyledProperty<ObservableCollection<BarViewModel>?> BarsSourceProperty =
  AvaloniaProperty.Register<QuxControl, ObservableCollection<BarViewModel>?>(nameof(BarsSource));

public static readonly StyledProperty<ICommand?> BazCommandProperty =
  AvaloniaProperty.Register<QuxControl, ICommand?>(nameof(BazCommand));

API breakdown

namespace CommunityToolkit.Mvvm.ComponentModel;

[AttributeUsage(AttributeTargets.Field | AttributeTargets.Property, AllowMultiple = false, Inherited = false)]
public sealed class AttachedPropertyAttribute : Attribute;

[AttributeUsage(AttributeTargets.Field | AttributeTargets.Property, AllowMultiple = false, Inherited = false)]
public sealed class DirectPropertyAttribute : Attribute;

[AttributeUsage(AttributeTargets.Field | AttributeTargets.Property, AllowMultiple = false, Inherited = false)]
public sealed class StyledPropertyAttribute : Attribute;

Usage example

QuxControl.cs

public partial class QuxControl : Panel
{
  [StyledProperty]
  public partial bool Foo { get; set; }

  [StyledProperty]
  public partial ObservableCollection<BarViewModel>? BarsSource { get; set; }

  [StyledProperty]
  public partial ICommand? BazCommand { get; set; }
}

MyProject.Views.QuxControl.g.cs

namespace MyProject.Views
{
  partial class QuxControl
  {
    /* ... */
    public partial bool Foo
    {
      get => GetValue(FooProperty);
      set => SetValue(FooProperty, value);
    }

    /* ... */
    public partial ObservableCollection<BarViewModel>? BarsSource
    {
      get => GetValue(BarsSourceProperty);
      set => SetValue(BarsSourceProperty, value);
    }

    /* ... */
    public partial ICommand? BazCommand
    {
      get => GetValue(BazCommandProperty);
      set => SetValue(BazCommandProperty, value);
    }

    /* ... */
    public static readonly StyledProperty<bool> FooProperty =
      AvaloniaProperty.Register<QuxControl, bool>(nameof(Foo));

    /* ... */
    public static readonly StyledProperty<ObservableCollection<BarViewModel>?> BarsSourceProperty =
      AvaloniaProperty.Register<QuxControl, ObservableCollection<BarViewModel>?>(nameof(BarsSource));

    /* ... */
    public static readonly StyledProperty<ICommand?> BazCommandProperty =
      AvaloniaProperty.Register<QuxControl, ICommand?>(nameof(BazCommand));
  }
}

Breaking change?

No

Alternatives

There are existing packages (https://github.com/jp2masa/Avalonia.PropertyGenerator, https://github.com/lucdem/AvaSourceGenerators) that don't entirely work in the proposed way.

Additional context

No response

Help us help you

No, just wanted to propose this