PropertyGenerator.Avalonia

Auto generate StyledProperty, DirectProperty, and AttachedProperty for Avalonia applications

StyledProperty

[GeneratedStyledProperty]
public partial int Count { get; set; }

Generated code:

StyledProperty<int> CountProperty = AvaloniaProperty.Register<MainWindow, int>(name: nameof(Count));
public partial int Count { get => GetValue(CountProperty); set => SetValue(CountProperty, value); }

---

[GeneratedStyledProperty(10)]
public partial int Count { get; set; }

Generated code:

Avalonia.StyledProperty<int> CountProperty = AvaloniaProperty.Register<MainWindow, int>(name: nameof(Count), defaultValue: 10);
public partial int Count { get => GetValue(CountProperty); set => SetValue(CountProperty, value); }

---

[GeneratedStyledProperty(
    DefaultValueCallback = nameof(DefaultValueCallback),
    DefaultValue = true,
    Validate = nameof(Validate),
    Coerce = nameof(Coerce),
    EnableDataValidation = true,
    Inherits = true,
    DefaultBindingMode = BindingMode.TwoWay)]
public partial bool? IsStarted { get; set; }

private static bool DefaultValueCallback()
{
    return true;
}
private static bool Validate(bool? value)
{
    return true;
}
private static bool? Coerce(AvaloniaObject x, bool? y)
{
    return true;
}

Generated code:

StyledProperty<bool?> IsStartedProperty = AvaloniaProperty.Register<MainWindow, bool?>(
	name: nameof(IsStarted), 
	defaultValue: DefaultValueCallback(), 
	validate: Validate,
	coerce: Coerce, 
	enableDataValidation: true,
	inherits: true, 
	defaultBindingMode:BindingMode.TwoWay);
public partial bool? IsStarted { get => GetValue(IsStartedProperty); set => SetValue(IsStartedProperty, value); }

DirectProperty

Similar in usage to StyledProperty generator

[GeneratedDirectProperty]
public partial IEnumerable? Items { get; set; }

---

You can directly initialize DirectProperty

[GeneratedDirectProperty]
public partial IEnumerable? Items { get; set; } = new AvaloniaList<object>();

---

You can also customize Getter and Setter for DirectProperty

[GeneratedDirectProperty(Getter = nameof(Getter), Setter = nameof(Setter))]
public partial IEnumerable? Items { get; set; }
public static IEnumerable? Getter(MainWindow o) => o.Items;
public static void Setter(MainWindow o, IEnumerable? v) => o.Items = v;

Generated code:

public static readonly DirectProperty<MainWindow, IEnumerable?> ItemsProperty
    = AvaloniaProperty.RegisterDirect<MainWindow, IEnumerable?>(
    name: nameof(Items),
    getter: Getter, 
    setter: Setter);

public partial IEnumerable? Items { get => field; set => SetAndRaise(ItemsProperty, ref field, value); }

Attached Property

Define attached properties on a partial class by using GenerateAttachedProperty<THost, TValue>:

[GenerateAttachedProperty<Control, string>("Tag")]
public partial class MainWindow : AvaloniaObject
{
}

Generated code:

public static readonly AttachedProperty<string> TagProperty = RegisterTagProperty();

public static string GetTag(Control host) => host.GetValue(TagProperty);
public static void SetTag(Control host, string value) => host.SetValue(TagProperty, value);

---

You can configure default value and registration options:

[GenerateAttachedProperty<Control, bool>("IsBusy",
    DefaultValueCallback = nameof(GetDefaultIsBusy),
    Validate = nameof(ValidateIsBusy),
    Coerce = nameof(CoerceIsBusy),
    Inherits = true,
    DefaultBindingMode = BindingMode.TwoWay)]
public partial class MainWindow : AvaloniaObject
{
    private static bool GetDefaultIsBusy() => true;
    private static bool ValidateIsBusy(bool value) => value;
    private static bool CoerceIsBusy(Control host, bool value) => value;
}

By default, attached property generation also emits these static partial callbacks:

static partial void OnIsBusyPropertyChanged(Control host, AvaloniaPropertyChangedEventArgs e);
static partial void OnIsBusyPropertyChanged(Control host, bool newValue);
static partial void OnIsBusyPropertyChanged(Control host, bool oldValue, bool newValue);

Apply DoNotGenerateOnPropertyChangedAttribute to disable those callbacks.

OnPropertyChanged

By default, the generator will override OnPropertyChanged and generate property changed methods at the same time:

partial void OnCountPropertyChanged(int newValue);
partial void OnCountPropertyChanged(int oldValue, int newValue);
partial void OnCountPropertyChanged(AvaloniaPropertyChangedEventArgs e);

partial void OnPropertyChangedOverride(AvaloniaPropertyChangedEventArgs change);

protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
{
    base.OnPropertyChanged(change);
    switch (change.Property.Name)
    {
        case nameof(Count):
            OnCountPropertyChanged(change);
            OnCountPropertyChanged((int)change.NewValue);
            OnCountPropertyChanged((int)change.OldValue, (int)change.NewValue);
            break;
    }
	OnPropertyChangedOverride(change);
}

You can still handle all property changes by using OnPropertyChangedOverride method.

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To generate property changed methods for properties in base class, you can use GenerateOnPropertyChangedAttribute on target class:

[GenerateOnPropertyChanged(nameof(Height))]
public partial class MainWindow : Window
{ ... }

---

To disable this feature, use DoNotGenerateOnPropertyChangedAttribute for class or assembly:

[DoNotGenerateOnPropertyChanged]
public partial class MainWindow : Window
{ ... }

[assembly: DoNotGenerateOnPropertyChanged]

Diagnostics

Rule ID	Severity	Area	Notes
PGA1001	Error	Styled/Direct	invalid property declaration shape for generated property.
PGA1002	Error	Styled/Direct	containing type must inherit AvaloniaObject.
PGA1003	Error	Styled/Direct	callback method not found.
PGA1004	Error	Styled/Direct	callback method signature invalid.
PGA1005	Error	Direct	invalid direct getter/setter method reference.
PGA1006	Error	Attached	invalid attached property name.
PGA1007	Error	All generators	containing type must be partial.
PGA1008	Warning	Attached	duplicate attached property name on owner.
PGA1009	Warning	OnPropertyChanged	GenerateOnPropertyChanged target property not found.
PGA1010	Warning	OnPropertyChanged	GenerateOnPropertyChanged disabled.