C#virtual,abstract,override,new,sealed

virtual:使用此关键字,可以使其在派生类中被重写.

abstract:抽象方法,由子类重写,或继续为抽象方法存在,并由其子子类实现.

override: 重写父类方法,属性,或事件的抽象实现或虚方法.

new:显式隐藏从父类继承的成员.

后台代码:

public abstract class Animal
{
    public abstract void Eat();

    public virtual void Sleep()
    {
        HttpContext.Current.Response.Write("动物正在睡觉!<hr/>");
    }
}

public class Horse : Animal
{
    public override void Eat()
    {
        HttpContext.Current.Response.Write("马在吃草!<br/>");
    }

    public override void Sleep()
    {
        HttpContext.Current.Response.Write("马是站着睡觉!<hr/>");
    }
}

public class Cat : Animal
{
    public override void Eat()
    {
        HttpContext.Current.Response.Write("猫在吃食!<br/>");
    }

    public new void Sleep()
    {
        HttpContext.Current.Response.Write("猫是趴着睡觉的!<hr/>");
    }
}

前台调用	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(); }

补充:

当sealed修饰方法时,sealed必须与override一起使用.

sealed将使您能够允许类从您的类继承，并防止它们重写特定的虚方法或虚属性

public class Cat : Animal
{
    public sealed override void Eat()
    {
        HttpContext.Current.Response.Write("猫在吃食!<br/>");
    }

    public new void Sleep()
    {
        HttpContext.Current.Response.Write("猫是趴着睡觉的!<hr/>");
    }
}

public class LitCat : Cat
{
    public new void Sleep()
    {
        HttpContext.Current.Response.Write("猫是趴着睡觉的!<hr/>");
    }
}

此时,在LitCat类中,就不会出现override Eat方法了.