繼承實際是一個類對另一個類的擴展，後者稱之為基類，前者稱之為子類。繼承就是子類擁有基類的一切屬性和方法，子類還可以增加屬性和方法。但是子類不能去掉父類的屬性和方法。
當然這裡還要提到修飾符的問題，子類擁有基類的所有屬性和方法，不意味著子類可以任意訪問繼承的這些屬性和方法。子類只能訪問到public和protected修飾的屬性和方法，其余無法直接訪問。還有一個就是static的屬性和方法是不能被繼承下來的，因為靜態類型之和類有關系與對象無關。
看代碼：
[csharp]
using System;
namespace YYS.CSharpStudy.MainConsole
{
public class YSchool
{
private int id = 0;
private string name = string.Empty;
public int ID
{
get
{
return this.id;
}
}
public string Name
{
get
{
return name;
}
}
/// <summary>
/// 構造器
/// </summary>
public YSchool()
{
this.id = 0;
this.name = @"清華大學附中";
}
/// <summary>
/// 構造器
/// </summary>
public YSchool(int id, string name)
{
this.id = id;
this.name = name;
}
/// <summary>
/// 構造器
/// </summary>
public YSchool(int id)
{
this.id = id;
this.name = @"陝師大附中";
}
}
public class YTeacher
{
private int id = 0;
private string name = string.Empty;
private YSchool school = null;
private string introDuction = string.Empty;
private string imagePath = string.Empty;
/// <summary>
/// 使用只讀屬性，因為是固有屬性。
/// </summary>
public int ID
{
get
{
return id;
}
}
public string Name
{
get
{
return name;
}
}
/// <summary>
/// 這幾個使用get/set屬性，因為這幾個屬性不是固有的，可以隨著某些條件改變的。
/// </summary>
public YSchool School
{
get
{
if (school == null)
{
school = new YSchool();
}
return school;
}
set
{
school = value;
}
}
public string IntroDuction
{
get
{
return introDuction;
}
set
{
introDuction = value;
}
}
public string ImagePath
{
get
{
return imagePath;
}
set
{
imagePath = value;
}
}
public YTeacher(int id, string name)
{
this.id = id;
this.name = name;
}
/// <summary>
/// 給學生講課的方法
/// </summary>
public void ToTeachStudents()
{
Console.WriteLine(string.Format(@"{0} 老師教育同學們： Good Good Study,Day Day Up!", this.name));
}
/// <summary>
/// 懲罰犯錯誤學生的方法
/// </summary>
/// <param name="punishmentContent"></param>
public void PunishmentStudents(string punishmentContent)
{
Console.WriteLine(string.Format(@"{0} 的{1} 老師讓犯錯誤的學生 {2}。", this.School.Name, this.name, punishmentContent));
}
}
/// <summary>
/// 男性老師，繼承自YTeacher
/// </summary>
public class MrTeacher : YTeacher
{
/// <summary>
/// 構造器，這裡要注意，YTeacher是沒有提供默認構造器的，
/// 所以子類必須要有構造器，並且和基類參數列表一致。
/// </summary>
/// <param name="id"></param>
/// <param name="name"></param>
public MrTeacher(int id, string name)
: base(id, name)
{
}
/// <summary>
/// 擴展的方法，刮胡子方法。
/// </summary>
public void Shave()
{
Console.WriteLine(string.Format(@"{0} 老師用飛科剃須刀刮胡子。",this.Name));
}
}
/// <summary>
/// 女性老師，繼承自YTeacher
/// </summary>
public class MisTeacher : YTeacher
{
/// <summary>
/// 構造函數
/// </summary>
/// <param name="id"></param>
/// <param name="name"></param>
public MisTeacher(int id, string name)
: base(id, name)
{
}
/// <summary>
/// 擴展方法，護膚的方法
/// </summary>
public void SkinCare()
{
Console.WriteLine(string.Format(@"{0} 老師用香奈兒護膚霜護膚。",this.Name));
}
}
}
using System;
namespace YYS.CSharpStudy.MainConsole
{
public class YSchool
{
private int id = 0;
private string name = string.Empty;
public int ID
{
get
{
return this.id;
}
}
public string Name
{
get
{
return name;
}
}
/// <summary>
/// 構造器
/// </summary>
public YSchool()
{
this.id = 0;
this.name = @"清華大學附中";
}
/// <summary>
/// 構造器
/// </summary>
public YSchool(int id, string name)
{
this.id = id;
this.name = name;
}
/// <summary>
/// 構造器
/// </summary>
public YSchool(int id)
{
this.id = id;
this.name = @"陝師大附中";
}
}
public class YTeacher
{
private int id = 0;
private string name = string.Empty;
private YSchool school = null;
private string introDuction = string.Empty;
private string imagePath = string.Empty;
/// <summary>
/// 使用只讀屬性，因為是固有屬性。
/// </summary>
public int ID
{
get
{
return id;
}
}
public string Name
{
get
{
return name;
}
}
/// <summary>
/// 這幾個使用get/set屬性，因為這幾個屬性不是固有的，可以隨著某些條件改變的。
/// </summary>
public YSchool School
{
get
{
if (school == null)
{
school = new YSchool();
}
return school;
}
set
{
school = value;
}
}
public string IntroDuction
{
get
{
return introDuction;
}
set
{
introDuction = value;
}
}
public string ImagePath
{
get
{
return imagePath;
}
set
{
imagePath = value;
}
}
public YTeacher(int id, string name)
{
this.id = id;
this.name = name;
}
/// <summary>
/// 給學生講課的方法
/// </summary>
public void ToTeachStudents()
{
Console.WriteLine(string.Format(@"{0} 老師教育同學們： Good Good Study,Day Day Up!", this.name));
}
/// <summary>
/// 懲罰犯錯誤學生的方法
/// </summary>
/// <param name="punishmentContent"></param>
public void PunishmentStudents(string punishmentContent)
{
Console.WriteLine(string.Format(@"{0} 的{1} 老師讓犯錯誤的學生 {2}。", this.School.Name, this.name, punishmentContent));
}
}
/// <summary>
/// 男性老師，繼承自YTeacher
/// </summary>
public class MrTeacher : YTeacher
{
/// <summary>
/// 構造器，這裡要注意，YTeacher是沒有提供默認構造器的，
/// 所以子類必須要有構造器，並且和基類參數列表一致。
/// </summary>
/// <param name="id"></param>
/// <param name="name"></param>
public MrTeacher(int id, string name)
: base(id, name)
{
}
/// <summary>
/// 擴展的方法，刮胡子方法。
/// </summary>
public void Shave()
{
Console.WriteLine(string.Format(@"{0} 老師用飛科剃須刀刮胡子。",this.Name));
}
}
/// <summary>
/// 女性老師，繼承自YTeacher
/// </summary>
public class MisTeacher : YTeacher
{
/// <summary>
/// 構造函數
/// </summary>
/// <param name="id"></param>
/// <param name="name"></param>
public MisTeacher(int id, string name)
: base(id, name)
{
}
/// <summary>
/// 擴展方法，護膚的方法
/// </summary>
public void SkinCare()
{
Console.WriteLine(string.Format(@"{0} 老師用香奈兒護膚霜護膚。",this.Name));
}
}
}[csharp]
using System;
namespace YYS.CSharpStudy.MainConsole
{
class Program
{
static void Main(string[] args)
{
MrTeacher mrTeacher = new MrTeacher(1, @"牛轟轟");
mrTeacher.ToTeachStudents();
mrTeacher.PunishmentStudents(@"背唐詩");
mrTeacher.Shave(); www.2cto.com
MisTeacher misTeacher = new MisTeacher(2, @"郝漂靓");
misTeacher.ToTeachStudents();
misTeacher.PunishmentStudents(@"默寫紅樓夢");
misTeacher.SkinCare();
Console.ReadKey();
}
}
using System;
namespace YYS.CSharpStudy.MainConsole
{
class Program
{
static void Main(string[] args)
{
MrTeacher mrTeacher = new MrTeacher(1, @"牛轟轟");
mrTeacher.ToTeachStudents();
mrTeacher.PunishmentStudents(@"背唐詩");
mrTeacher.Shave();
MisTeacher misTeacher = new MisTeacher(2, @"郝漂靓");
misTeacher.ToTeachStudents();
misTeacher.PunishmentStudents(@"默寫紅樓夢");
misTeacher.SkinCare();
Console.ReadKey();
}
}
結果：
繼承是面向對象的特性，它的好處是：
第一、做項目設計類時，繼承可以讓我們省略量代碼；
第二、符合面向對象中類的組織形式，在C#、java等高級面向對象語言中，都有一個object類，這是所有類的祖宗類，其他類都有他派生而來。
繼承需要注意一點，就是子類的構造器問題。程序運行過程是子類首先調用父類的構造器。如果子類沒有寫構造器，那麼就會調用父類的默認構造器。如果父類沒有默認的構造器，即父類寫了帶參數的構造器，那麼子類也就調用帶參數的那個構造器，不過需要指明是調用的哪個帶參數的構造器（見代碼中base）。
作者：yysyangyangyangshan
