//новый класс 
public static readonly DependencyProperty xx = DependencyProperty.Register("p1", typeof(Point), typeof(myline), new FrameworkPropertyMetadata(new Point()), new ValidateValueCallback(draw));

   public Point p1
        {
            set { SetValue(xx, value); }
            get { return (Point)GetValue(xx); }
        }
  static  bool draw(object value)
        {
          
                MessageBox.Show("sdf");
         
               return true;
        }
//часть кода канвы
Point p = new Point(9, 9);
    public void addline(myellipse el1,myellipse el2)
    {
        myline line = new myline();
        children.Add(line);
        
        base.AddLogicalChild(line);
        base.AddVisualChild(line);
        line.bind = new Binding("p");
        line.bind.Source =this;
    
        BindingOperations.SetBinding(line, myline.xx, line.bind);
}
   protected override void OnMouseMove(System.Windows.Input.MouseEventArgs e)
    {
        base.OnMouseMove(e);
 
            p = e.GetPosition(this); //тут не выскакивает событие "sdf"

}

 class myline:DrawingVisual
    {
public static readonly DependencyProperty xx = DependencyProperty.Register("p1", typeof(Point), typeof(myline), new FrameworkPropertyMetadata(new Point()), new ValidateValueCallback(draw));

   public Point p1
        {
            set { SetValue(xx, value); }
            get { return (Point)GetValue(xx); }
        }
  static  bool draw(object value)
        {
          
                MessageBox.Show("sdf");
         
               return true;
        }
}
public class MyVisualHost : Canvas
{
Point p = new Point(9, 9);
   public Point pp
    {
        set { p=value; }
        get { return p; }
    }
    public void addline(myellipse el1,myellipse el2)
    {
        myline line = new myline();
        children.Add(line);
        
        base.AddLogicalChild(line);
        base.AddVisualChild(line);
        line.bind = new Binding("pp");
        line.bind.Source =this;
    
        BindingOperations.SetBinding(line, myline.xx, line.bind);
}
   protected override void OnMouseMove(System.Windows.Input.MouseEventArgs e)
    {
        base.OnMouseMove(e);
 
            p = e.GetPosition(this); //тут не выскакивает событие "sdf"

}
}

public class BindingObject : DependencyObject
    {
        public DependencyProperty BindingValueProperty;
        public BindingObject()
        {
            BindingValueProperty =
                        DependencyProperty.Register("BindingValue", typeof(bool), typeof(BindingObject),
                        new PropertyMetadata(new PropertyChangedCallback(OnBindingValueChanged)));
        }
        public  void OnBindingValueChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)
        {
            MessageBox.Show("s");//  не срабатывает
        }
        public bool BindingValue
        {
            get { return (bool)GetValue(BindingValueProperty); }
            set { this.SetValue(BindingValueProperty, value); }
        }
    }

 public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }
        Binding binding;
        BindingObject obj;
        bool p;
        public bool pp
        {

            set { p = value; }
            get { return p; }
      

            }
        private void button1_Click(object sender, RoutedEventArgs e)
        {
            binding = new Binding("pp");
            binding.Source = this;
            binding.Mode = BindingMode.OneWay;
           obj = new BindingObject();
            BindingOperations.SetBinding(obj, obj.BindingValueProperty, binding);
           
            
        }

        private void checkBox1_Checked(object sender, RoutedEventArgs e)
        {
            if (p == true)
                pp = false;
            else
                pp = true;
        }
    }