抽象类

 [Auth(Age = 15)]
    public abstract class Father : GrandFather
    {
        public Father()
        {
            this.Wr();
        }

        public abstract void  Wr () ;

选择性实现

   public class Student : Father
    {
        public Student():base()
        {

        }

        public override void Wr()
        {
            Console.WriteLine("saic");
        }