10_9_2从类MyClass中派生一个类MyDervedClass,重写GetString(),使用该方法的基类实现代码从基类中返回一个字符串,但在返回的字符串中添加文本"(output fro)"

//file name MyClass.csusing System;using System.Collections.Generic;using System.Linq;using System.Text;namespace _10_9_1{    class MyClass    {        private string myString;         public string ContainedString        {                        set            {                myString = value;            }        }        public MyClass() { }        public MyClass(string str)        {            myString = str;        }        public virtual string GetString()        {            return "this base class string.";        }    }}//file name MyDerivedClass.csusing System;using System.Collections.Generic;using System.Linq;using System.Text;namespace _10_9_1{    class MyDerivedClass : MyClass    {        public override string GetString()        {            return base.GetString()+"output from derived class.";        }    }}//-----------------------------------------//file name Program.csusing System;using System.Collections.Generic;using System.Linq;using System.Text;namespace _10_9_1{    class Program    {        static void Main(string[] args)        {            MyDerivedClass DerClass = new MyDerivedClass();            Console.WriteLine(DerClass.GetString());            Console.ReadKey();        }    }}