C# 的关键字系列

[来源] 达内    [编辑] 达内   [时间]2012-11-13

用于修饰类,方法,属性和字段的关键字

用于修饰类,方法,属性和字段的关键字:

< p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 25EF2F35FEAF4121BB818989474E8D99

< p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">首先从最简单的private,protected,internal,public  解释。

< p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">public 和internal 修饰类。

< p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">public,protected,private 修饰方法。

< p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 

< p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">修饰类的时候:

< p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">public 代表公开,也就是所有程序集都可以访问这个类。

< p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> internal 代表内部的,也就是只有在同一程序集中才能访问这个类,一般而言同一程序集就是同一个dll。

< p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 

< p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">修饰方法的时候:

< p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">public 代表公开,也就是所有的类都可以访问这个方法。

< p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">protected 代表受保护的,也就是只有我的子类才能访问这个方法。

< p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">private 代表私有的,也就是只有我才能访问这个方法。

< p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 

< p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">接着我们来讨论下const,readonly  的区别:

< p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">首先两者都是常量, 不同的是const 是编译时常量,readonly是运行时常量

< p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 编译时常量:在编译的时候,值就已经是常量了,任何使用该变量的地方都会被替换成常量值。

< p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">运行时常量:在运行的时候,值不能够被修改。

< p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 

< p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">public  class Test
{
    public const  string constStr = "this is a test";
    public readonly  string readonlyStr = "this can't be modified in runtime time";
    
    public void Method1()
    {
        string s1 = constStr; // 在编译的时候,这句话就会被替换成 string s1 = "this is a test";
        readonlyStr = "error"; 
        //尝试修改readonlyStr,无法通过编译,
        //抛出错误:readonly 字段只有在构造函数和初始化的时候才能修改。
    }
}

< p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 55CED59AEF3A442CAD539A7F94A09CA9

< p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">OK,现在我们讨论下abstract, virtual , new , override  关键字:

< p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 

< p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">首先abstract  代表的是抽象,abstract 可以修饰类和方法。

< p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">修饰类的时候:

< p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">这个时候叫做抽象类,抽象类有下列性质:

< ul style="margin: 0px 0px 0px 45px; padding: 0px; list-style-type: disc; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">
  • 抽象类不能实例化。

  • 抽象类可以包含抽象方法和抽象访问器,访问器实际上也是方法

  • 不能用 sealed修饰符修饰抽象类,因为这两个修饰符的含义是相反的。 采用 sealed 修饰符的类无法继承,而 abstract 修饰符要求对类进行继承。

  • 从抽象类派生的非抽象类必须包括继承的所有抽象方法和抽象访问器的实际实现。

  • < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 

    < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">修饰方法的时候:

    < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">这个时候叫做抽象方法,性质如下:

    < ul style="margin: 0px 0px 0px 45px; padding: 0px; list-style-type: disc; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">
  • 抽象方法是隐式的虚方法(用virtual 修饰方法的叫做虚方法)。

  • 只允许在抽象类中使用抽象方法声明,只要使用抽象方法,那么这个就是抽象类。

  • 因为抽象方法声明不提供实际的实现,所以没有方法体;方法声明只是以一个分号结束,并且在签名后没有大括号 ({ })。 例如:

    public abstract void MyMethod();
    

    实现由一个重写方法override 提供,此重写方法是非抽象类的一个成员。

  • 在抽象方法声明中使用 static 或 virtual 修饰符是错误的,因为抽象方法需要被重写,所以不能用static修饰,因为抽象方法是隐式的虚方法,所以不能用virtual修饰。

  • 除了在声明和调用语法上不同外,抽象属性的行为与抽象方法一样,属性本质上是方法

  • < ul style="margin: 0px 0px 0px 45px; padding: 0px; list-style-type: disc; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">
  • 在静态属性上使用 abstract 修饰符是错误的。

  • 在派生类中,通过包括使用 override 修饰符的属性声明,可以重写抽象的继承属性。

  • < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 

    < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">virtual  关键字代表虚拟的,虚的,修饰的是方法。

    < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">修饰方法的时候:

    < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 这个时候叫做虚方法,虚方法代表这个方法是虚的,这个方法可能没有实现,这个方法可以被重写。

    < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">关键的一句话是:这个方法可以被重写。

    < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 这代表,如果这个方法想要被重写,被override,那么它就必须是一个虚方法,因为abstract修饰的方法是隐式的虚方法,所以 abstract和virtual 修饰的方法可以被override。

    < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 

    < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 

    < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 

    < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">override  关键字代表重写,修饰的是方法。

    < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> override 方法提供从基类继承的成员的新实现。 由 override 声明重写的方法称为重写基方法。 重写的基方法必须与 override 方法具有相同的签名。

    < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">修饰方法的时候:

    < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">1:不能重写非虚方法或静态方法。 重写的基方法必须是 virtual、abstract 或 override 的。

    < blockquote style="margin: 10px 0px 10px 25px; padding: 5px 10px; background-image: none; background-color: rgb(255, 255, 255); border: 2px solid rgb(239, 239, 239); color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial; ">

    override 方法和 virtual 方法必须具有相同的访问级别修饰符。

    < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">2:您不能使用 new、static 或 virtual 修饰符来修改 override 方法。

    < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 3:重写属性声明必须指定与继承属性完全相同的访问修饰符、类型和名称,并且被重写的属性必须

    < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">     是 virtual、abstract 或 override 的。

    < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 

    < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">new  关键字代表隐藏,修饰的是方法。

    < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> new 和override 的区别是,new 是隐藏父类方法,这就好比告诉别人,这个方法和父类的方法是两个不同的方法,只是他们的签名刚好相同罢了,override 则不同,override 告诉别人,以后用我的 instance调用的就是我的方法,用父类的instance 调用的就是父类的方法。

    < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 

    < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">总结下:abstract,virtual,override,new 的关系。

    < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">override 的方法必须是abstract ,virtual, override 的。

    < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">abstract 的方法是隐式的virtual 方法。

    < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">virtual 的方法代表这个方法可以被重写,当然你也可以不重写它。

    < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">abstract的方法代表这个方法是必须被重写的方法。

    < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> new 的方法代表这个方法和父类的没关系,是一个新的“new” 方法,只是刚好签名相同罢了。

    < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 

    < p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">最后一道题: 

    < div style="margin: 5px 0px; padding: 5px; background-color: rgb(245, 245, 245); font-family: 'Courier New'; font-size: 12px; border: 1px solid rgb(204, 204, 204); overflow: auto; color: rgb(51, 51, 51); font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; " class="cnblogs_code">
    
    
    
    class A { 	public
     virtual void
     F() 	{ 		Console.WriteLine("A.F
    "); 	} } class
    
     B : A { 	public override
     void
     F() 	{ 		Console.WriteLine("B.F
    
    "); 	} } class C : B { 	
    new
    
     public virtual
     void F() { Console.WriteLine("
    C.F
    
    "); } } class D : C { 	
    public
    
     override void
     F() { Console.WriteLine("D.F
    "); } } class
    
     Program2 { 	static void
     Main() 	{ 		D d = new D(); 		A a = d; B b = d; 		C c = d; a.F(); b.F(); 		c.F(); 		d.F(); 	} }

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