c#父类对象引用指向子类与方法重写

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace csharp_test
{
    class Parentclass
    {
        public Parentclass()
        {
            Console.WriteLine("this is parentclass's cunstructor");
        }

        public  void print()
        {
            Console.WriteLine("this is parent 's print");
        }
    }

    class Childclass : Parentclass
    {
        public Childclass()
        {
            Console.WriteLine("this is childclass's cunstructor");
        }

        public  void print()
        {
            Console.WriteLine("this is child 's print");
        }

        static void Main(string []args)
        {
            Parentclass p = new Parentclass();
            p.print();
            Parentclass c = new Childclass();
            c.print();
        }
    }
}

this is parentclass's cunstructor
this is parent 's print
this is parentclass's cunstructor
this is childclass's cunstructor
this is parent 's print
运行结果如上，可见，如果声明一个父类对象指向子类对象，会调用父类的方法。

如果将子类的print方法删除，仍然会调用父类的方法，但是如果删除父类的方法，就会报错。

 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace csharp_test
{
    class Parentclass
    {
        public Parentclass()
        {
            Console.WriteLine("this is parentclass's cunstructor");
        }

        public  void print()
        {
            Console.WriteLine("this is parent 's print");
        }
    }

    class Childclass : Parentclass
    {
        public Childclass()
        {
            Console.WriteLine("this is childclass's cunstructor");
        }

        public  void print()
        {
            Console.WriteLine("this is child 's print");
        }

        static void Main(string []args)
        {
            Parentclass p = new Parentclass();
            p.print();
            Childclass c = new Childclass();
            c.print();
        }
    }
}

this is parentclass's cunstructor
this is parent 's print
this is parentclass's cunstructor
this is childclass's cunstructor
this is child 's print

运行结果如上，可见，如果声明子类对象指向子类对象，会调用子类的方法。

如果删除了子类方法，那么就会自动调用父类的print方法。

 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace csharp_test
{
    class Parentclass
    {
        public Parentclass()
        {
            Console.WriteLine("this is parentclass's cunstructor");
        }

        public virtual void print()
        {
            Console.WriteLine("this is parent 's print");
        }
    }

    class Childclass : Parentclass
    {
        public Childclass()
        {
            Console.WriteLine("this is childclass's cunstructor");
        }

        public override void print()
        {
            Console.WriteLine("this is child 's print");
        }

        static void Main(string []args)
        {
            Parentclass p = new Parentclass();
            p.print();
            Parentclass c = new Childclass();
            c.print();
        }
    }
}

this is parentclass's cunstructor
this is parent 's print
this is parentclass's cunstructor
this is childclass's cunstructor
this is child 's print

结果如上所示，如果子类重写了父类的方法，那么尽管父类是指向子类的，但是仍然会调用子类的方法。