DependencyPropertyGenerator

While standard C# properties usually avoid new expressions in defaults, this generator allows them via the DefaultValueExpression property. This is useful for initializing properties with new objects or structs.

If the type is in a different namespace than the attribute, you must provide the fully qualified name.

public readonly record struct Data();

[AttachedDependencyProperty<object, TreeView>("SelectedItem", DefaultValueExpression = "new Data()",
// Note: Use full namespace if Data is not in the same namespace as the attribute
// DefaultValueExpression = "MyNamespace.Data()")]

Use the [DependencyProperty] attribute on a partial class to automatically generate the DependencyProperty field, the property wrapper (getter/setter), and change notification hooks. You can specify the property name, DefaultValue, Category, and Description within the attribute.

To handle property changes, implement the partial void On[PropertyName]Changed(oldValue, newValue) method in your class.

[DependencyProperty<bool>("IsSpinning", DefaultValue = true, Category = "Category", Description = "Description")]
public partial class MyControl : UserControl
{
    // Optional: Handle changes
    partial void OnIsSpinningChanged(bool oldValue, bool newValue)
    {
    }
}

If automatic platform detection fails, you can manually define constants in your .csproj file to help the generator identify the target platform:

<PropertyGroup>
  <DefineConstants>$(DefineConstants);HAS_UNO</DefineConstants>
  <DefineConstants>$(DefineConstants);HAS_UNO_WINUI</DefineConstants>
  <DefineConstants>$(DefineConstants);HAS_AVALONIA</DefineConstants>
</PropertyGroup>

There are two ways to add documentation:

1. Simple: Use the Description parameter in the attribute. This adds a System.ComponentModel.Description attribute and populates the XML documentation.
2. Advanced: Use XmlDocumentation or PropertyXmlDocumentation attribute properties to provide raw XML text for the DependencyProperty or the property's getter/setter.

Use the [AttachedDependencyProperty] attribute on a static partial class to generate attached properties. This includes the DependencyProperty field, Get[PropertyName] and Set[PropertyName] methods, and change notification hooks.

You can specify the DefaultBindingMode (e.g., DefaultBindingMode.TwoWay) via the attribute.

To handle changes, implement the static partial void On[PropertyName]Changed(sender, oldValue, newValue) method.

[AttachedDependencyProperty<object, TreeView>("SelectedItem", DefaultBindingMode = DefaultBindingMode.TwoWay)]
public static partial class TreeViewExtensions
{
    // Optional: Handle changes
    static partial void OnSelectedItemChanged(TreeView sender, object? oldValue, object? newValue)
    {
    }
}

To use the generic versions of the attributes provided by this library, you must set your C# language version to preview in your project file:

<LangVersion>preview</LangVersion>

The generator can automatically manage event subscriptions (attaching/detaching) for properties that depend on specific events. Use the BindEvent parameter in the attribute and provide the name of the event (e.g., nameof(Grid.MouseWheel)).

The generator will create OnBindEventPropertyChanged_BeforeBind and OnBindEventPropertyChanged_AfterBind partial methods that you can use to wrap the subscription logic.

[AttachedDependencyProperty<object, Grid>("BindEventProperty", BindEvent = nameof(Grid.MouseWheel))]
public static partial class GridExtensions
{
    // This method is called during the subscription lifecycle
    private static void OnBindEventPropertyChanged_MouseWheel(object? sender, System.Windows.Input.MouseWheelEventArgs args)
    {
    }
}