第二单元代码

第一题
using System;
namespace Test2_1
{
/// <summary>
/// Class1 的摘要说明。

/// </summary>
class Class1
{
/// <summary>
/// 应用程序的主入口点。

/// </summary>
[STAThread]
static void Main(string[] args)
{
//
// TODO: 在此处添加代码以启动应用程序
//
Animal ani =new Animal ();
Console.WriteLine (ani.Introduce());
Dog dog=new Dog ();
Console.WriteLine (dog.Introduce());
Cat cat=new Cat ();
Console.WriteLine (cat.Introduce ());
Console.WriteLine ("按回车键结束");
Console.Read ();
}
}
}
using System;
namespace Test2_1
{
/// <summary>
/// Animal 的摘要说明。

/// </summary>
{
public Animal()
{
Sex=false;
}
private bool m_sex;
private int m_age;
public bool Sex
{
get
{
return m_sex;
}
set
{
m_sex=value;
}
}
public int Age
{
get
{
return m_age;
}
set
{
m_age=value;
}
}
public virtual string Introduce() {
if(Sex)
return"This is a male Animal!";
else
return"This is a female Animal!"; }
}
public class Cat:Test2_1.Animal
{
{
}
public override string Introduce()
{
if (Sex)
return"This is a male Cat!";
else
return"This is a female Cat!";
}
}
public class Dog:Test2_1.Animal
{
public Dog()
{
Sex=true;
}
public override string Introduce()
{
if (Sex)
return"This is a male Dog!";
else
return"This is a female Dog!";
}
}
}
第二题
using System;
namespace Test2_2
{
/// <summary>
/// Class1 的摘要说明。

/// </summary>
class Class1
{
/// <summary>
/// 应用程序的主入口点。

/// </summary>
[STAThread]
static void Main(string[] args)
{
Student std =new Student ();
Console.WriteLine (std.Introduce ());
Undergraduate ugd = new Undergraduate ();
ugd.Grade =4;
Console.WriteLine (ugd.Introduce ());
Graduate ate=new Graduate ();
ate.Grade =4;
Console.WriteLine (ate.Introduce ());
Console.WriteLine ("按回车键结束");
Console.Read ();
}
}
}
using System;
namespace Test2_2
{
/// <summary>
/// Student 的摘要说明。

/// </summary>
public class Student
{
public Student()
{
m_grade=1;
}
private string m_name;
private int m_grade;
public string Name
{
get
{
return m_name;
}
set
{
m_name=value;
}
}
public int Grade
{
get
{
return m_grade;
}
set
{
m_grade=value;
}
}
public virtual string Introduce()
{
return "This is a student of grade"+Grade;
}
}
}
public class Undergraduate:Test2_2.Student
{
public Undergraduate()
{
}
public override string Introduce()
{
if( Grade>=1&&Grade<=4)
return "This is an undergraduate of grade"+Grade;
else
return "No such grade";
}
}
public class Graduate:Test2_2.Student
{
public Graduate()
{
}
public override string Introduce()
{
if( Grade>=1&&Grade<=3)
return "This is an Graduate of grade"+Grade;
else
return "No such grade";
}
}。