C#–virtual,abstract,override,new,sealed

virtual:使用此關鍵字,可以使其在衍生類別中被重寫.

abstract:抽象方法,由子類重寫,或繼續為抽象方法存在,並由其子子類實現.

override: 重寫父類方法,屬性,或事件的抽象實現或虛方法.

new:顯式隱藏從父類繼承的成員.

 

後台代碼:

public abstract class Animal{    public abstract void Eat();    public virtual void Sleep()    {        HttpContext.Current.Response.Write("動物正在睡覺!<hr/>");    }}public class Horse : Animal{    public override void Eat()    {        HttpContext.Current.Response.Write("馬在吃草!<br/>");    }    public override void Sleep()    {        HttpContext.Current.Response.Write("馬是站著睡覺!<hr/>");    }}public class Cat : Animal{    public override void Eat()    {        HttpContext.Current.Response.Write("貓在吃食!<br/>");    }    public new void Sleep()    {        HttpContext.Current.Response.Write("貓是趴著睡覺的!<hr/>");    }}

前台調用	效果
protected void Page_Load(object sender, EventArgs e) { Animal an1 = new Horse(); an1.Eat(); an1.Sleep(); Animal an2 = new Cat(); an2.Eat(); an2.Sleep(); Horse an3 = new Horse(); an3.Eat(); an3.Sleep(); Cat an4 = new Cat(); an4.Eat(); an4.Sleep(); }

 

補充:

當sealed修飾方法時,sealed必須與override一起使用.

sealed將使您能夠允許類從您的類繼承，並防止它們重寫特定的虛方法或虛屬性

public class Cat : Animal{    public sealed override void Eat()    {        HttpContext.Current.Response.Write("貓在吃食!<br/>");    }    public new void Sleep()    {        HttpContext.Current.Response.Write("貓是趴著睡覺的!<hr/>");    }}public class LitCat : Cat{    public new void Sleep()    {        HttpContext.Current.Response.Write("貓是趴著睡覺的!<hr/>");    }}

此時,在LitCat類中,就不會出現override Eat方法了.