Binding 依赖属性定义

class BackgroundPath:Image
    {
        public event PropertyChangedEventHandler PropertyChanged;
        static BackgroundPath()
        {
            BindSourceProperty =
            DependencyProperty.Register("BindSource",
            typeof(BitmapImage),
            typeof(BackgroundPath),
            new PropertyMetadata(new BitmapImage(new Uri(PathShow.ImageSelected)), OnBitmapImageChanged));
        }

        public BitmapImage BindSource
        {
            get
            {   return (BitmapImage)GetValue(BindSourceProperty);}
            set
            {   SetValue(BindSourceProperty, value);}
        }
        public static DependencyProperty BindSourceProperty { private set; get; }

        static void OnBitmapImageChanged(DependencyObject obj, DependencyPropertyChangedEventArgs args)
        {
            (obj as BackgroundPath).OnBitmapImageChanged(args);
        }

        void OnBitmapImageChanged(DependencyPropertyChangedEventArgs args)
        {
            if (args.Property == BindSourceProperty)
                BindSource = (BitmapImage)args.NewValue;
        }
    }


 Binding bind = new Binding()
            {
                Source = new BackgroundPath(),
                Path = new PropertyPath("BindSource")
            };
            faceImge.SetBinding(Image.SourceProperty,bind);