WPF附加属性

public class School
    {
        public static int GetGrade(DependencyObject obj)
        {
            return (int)obj.GetValue(GradeProperty);
        }

        public static void SetGrade(DependencyObject obj, int value)
        {
            obj.SetValue(GradeProperty, value);
        }

        // Using a DependencyProperty as the backing store for Grade.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty GradeProperty =
            DependencyProperty.RegisterAttached("Grade", typeof(int), typeof(School), new PropertyMetadata(0)); 
    }

 //自定义附加属性的使用
  Human human = new Human();
  School.SetGrade(human, 6);
  int grade = School.GetGrade(human);
  MessageBox.Show(grade.ToString());