docs-desktop/dotnet-desktop-guide/net/wpf/properties/snippets/custom-dependency-properties/csharp/MainWindow.xaml.cs

using System;
using System.Diagnostics;
using System.Windows;

namespace CodeSampleCsharp
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml.
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();

            // Test code.
            Aquarium aquarium = new();
            aquarium.AquariumGraphic = new Uri("http://www.contoso.com/aquarium-graphic-new.jpg");
            Debug.WriteLine($"Aquarium graphic: {aquarium.AquariumGraphic}");

            // Output:
            // OnUriChanged: http://www.contoso.com/aquarium-graphic-new.jpg
            // Aquarium graphic: http://www.contoso.com/aquarium-graphic-new.jpg
        }
    }

    public class Aquarium : DependencyObject
    {
        //<RegisterDependencyPropertyWithWrapper>
        //<RegisterDependencyProperty>
        // Register a dependency property with the specified property name,
        // property type, owner type, and property metadata. Store the dependency
        // property identifier as a public static readonly member of the class.
        public static readonly DependencyProperty AquariumGraphicProperty =
            DependencyProperty.Register(
              name: "AquariumGraphic",
              propertyType: typeof(Uri),
              ownerType: typeof(Aquarium),
              typeMetadata: new FrameworkPropertyMetadata(
                  defaultValue: new Uri("http://www.contoso.com/aquarium-graphic.jpg"),
                  flags: FrameworkPropertyMetadataOptions.AffectsRender,
                  propertyChangedCallback: new PropertyChangedCallback(OnUriChanged))
            );
        //</RegisterDependencyProperty>

        // Declare a read-write property wrapper.
        public Uri AquariumGraphic
        {
            get => (Uri)GetValue(AquariumGraphicProperty);
            set => SetValue(AquariumGraphicProperty, value);
        }
        //</RegisterDependencyPropertyWithWrapper>

        private static void OnUriChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs e)
        {
            Uri value = (Uri)dependencyObject.GetValue(AquariumGraphicProperty);
            Debug.WriteLine($"OnUriChanged: {value}");
        }
    }
}