defining-wpf-dependencyproperty

WPF DependencyProperty Patterns

Defining dependency properties for data binding, styling, animation, and property value inheritance.

Advanced Patterns: See ADVANCED.md for value inheritance, metadata override, and event integration.

1. DependencyProperty Overview

Standard CLR Property:
    private string _name;
    public string Name { get => _name; set => _name = value; }

DependencyProperty:
    public static readonly DependencyProperty NameProperty = ...
    public string Name { get => (string)GetValue(NameProperty); set => SetValue(NameProperty, value); }

Benefits:
    ✅ Data Binding
    ✅ Styling & Templating
    ✅ Animation
    ✅ Property Value Inheritance
    ✅ Default Values
    ✅ Change Notifications
    ✅ Value Coercion
    ✅ Validation

2. Basic DependencyProperty

2.1 Standard Registration

namespace MyApp.Controls;

using System.Windows;
using System.Windows.Controls;

public class MyControl : Control
{
    // 1. Register DependencyProperty
    public static readonly DependencyProperty TitleProperty = DependencyProperty.Register(
        name: nameof(Title),
        propertyType: typeof(string),
        ownerType: typeof(MyControl),
        typeMetadata: new PropertyMetadata(defaultValue: string.Empty));

    // 2. CLR property wrapper
    public string Title
    {
        get => (string)GetValue(TitleProperty);
        set => SetValue(TitleProperty, value);
    }
}

2.2 With FrameworkPropertyMetadata

public static readonly DependencyProperty ValueProperty = DependencyProperty.Register(
    name: nameof(Value),
    propertyType: typeof(double),
    ownerType: typeof(MyControl),
    typeMetadata: new FrameworkPropertyMetadata(
        defaultValue: 0.0,
        flags: FrameworkPropertyMetadataOptions.AffectsRender |
               FrameworkPropertyMetadataOptions.BindsTwoWayByDefault,
        propertyChangedCallback: OnValueChanged,
        coerceValueCallback: CoerceValue),
    validateValueCallback: ValidateValue);

public double Value
{
    get => (double)GetValue(ValueProperty);
    set => SetValue(ValueProperty, value);
}