WPF：如何使基类的依赖属性只读_

Question

我有课 public class NavigableViewport3D : Viewport3D。该类应隐藏Viewport3D.Camera 属性，使其变为只读。这是我目前所拥有的：

public class NavigableViewport3D : Viewport3D
{
    protected static readonly DependencyPropertyKey CameraPropertyKey = DependencyProperty.RegisterReadOnly(
        "Camera",
        typeof(Camera),
        typeof(NavigableViewport3D),
        new PropertyMetadata()
        );
    public static readonly new DependencyProperty CameraProperty = CameraPropertyKey.DependencyProperty;

    public new Camera Camera
    {
        get
        {
            return base.Camera;
        }
        protected set
        {
            base.Camera = value;
        }
    }
}

但我也希望 NavigableViewport3D.CameraProperty 始终返回与 Viewport3D.CameraProperty/base.Camera 相同的值... 如果没有依赖属性，我会这样做：

public class NavigableViewport3D : Viewport3D
{
    public new Camera Camera
    {
        get
        {
            return base.Camera;
        }
        protected set
        {
            base.Camera = value;
        }
    }

}

这是一种应该完成双向交换的丑陋方式：

public class NavigableViewport3D : Viewport3D
{
    protected static readonly DependencyPropertyKey CameraPropertyKey = DependencyProperty.RegisterReadOnly(
        "Camera",
        typeof(Camera),
        typeof(NavigableViewport3D),
        new PropertyMetadata(new PropertyChangedCallback(
            delegate(DependencyObject depO, DependencyPropertyChangedEventArgs e)
            {
                if (e.OldValue != e.NewValue) //Not sure whether this is needed
                    depO.SetValue(Viewport3D.CameraProperty, e.NewValue);
            }
        )));
    public static readonly new DependencyProperty CameraProperty = CameraPropertyKey.DependencyProperty;

    public new Camera Camera
    {
        get
        {
            return this.Camera;
        }
        protected set
        {
            this.Camera = value;
        }
    }        

    public NavigableViewport3D()
    {
        Viewport3D.CameraProperty.AddOwner(
            typeof(NavigableViewport3D), 
            new PropertyMetadata(new PropertyChangedCallback(
                delegate(DependencyObject depO, DependencyPropertyChangedEventArgs e)
                {
                    var nv3d = depO as NavigableViewport3D;
                    if (nv3d == null)
                        return;
                    nv3d.SetValue(CameraPropertyKey, e.NewValue);
                }
        )));
    }
}

我真的希望有更好的方法来完成这个...有什么建议吗？

Answer 1

这个怎么样：

namespace WpfApplication1
{
    /// <summary>
    /// Interaction logic for Window1.xaml
    /// </summary>
    public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();
        }
    }

    public class NavigableViewport3D : Viewport3D
    {
        public static readonly new DependencyProperty CameraProperty;

        static NavigableViewport3D()
        {
            NavigableViewport3D.CameraProperty = Viewport3D.CameraProperty.AddOwner( typeof( NavigableViewport3D ) );
        }
    }
}