override 修饰符

override（C# 参考）

要扩展或修改继承的方法、属性、索引器或事件的抽象实现或虚实现，必须使用 override 修饰符。

abstract class ShapesClass

{

    abstract public int Area();

}

class Square : ShapesClass

{

    int side = ;

    public Square(int n)

    {

        side = n;

    }

    // Area method is required to avoid

    // a compile-time error.

    public override int Area()

    {

        return side * side;

    }

    static void Main()

    {

        Square sq = new Square();

        Console.WriteLine("Area of the square = {0}", sq.Area());

    }

    interface I

    {

        void M();

    }

    abstract class C : I

    {

        public abstract void M();

    }

}

// Output: Area of the square = 144

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。
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 修饰的。
override 声明不能更改 virtual 方法的可访问性。 override 方法和 virtual 方法必须具有相同的访问级别修饰符。
您不能使用 new、static 或 virtual 修饰符来修改 override 方法。
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是 virtual、abstract 或 override 修饰的。

此示例定义了一个名为 Employee 的基类和一个名为 SalesEmployee 的派生类。 SalesEmployee 类包括一个额外的属性 salesbonus，并重写方法 CalculatePay 以便将该属性考虑在内。
C#

class TestOverride

{

    public class Employee

    {

        public string name;

        // Basepay is defined as protected, so that it may be

        // accessed only by this class and derrived classes.

        protected decimal basepay;

        // Constructor to set the name and basepay values.

        public Employee(string name, decimal basepay)

        {

            this.name = name;

            this.basepay = basepay;

        }

        // Declared virtual so it can be overridden.

        public virtual decimal CalculatePay()

        {

            return basepay;

        }

    }

    // Derive a new class from Employee.

    public class SalesEmployee : Employee

    {

        // New field that will affect the base pay.

        private decimal salesbonus;

        // The constructor calls the base-class version, and

        // initializes the salesbonus field.

        public SalesEmployee(string name, decimal basepay,

                  decimal salesbonus) : base(name, basepay)

        {

            this.salesbonus = salesbonus;

        }

        // Override the CalculatePay method

        // to take bonus into account.

        public override decimal CalculatePay()

        {

            return basepay + salesbonus;

        }

    }

    static void Main()

    {

        // Create some new employees.

        SalesEmployee employee1 = new SalesEmployee("Alice",

                      , );

        Employee employee2 = new Employee("Bob", );

        Console.WriteLine("Employee4 " + employee1.name +

                  " earned: " + employee1.CalculatePay());

        Console.WriteLine("Employee4 " + employee2.name +

                  " earned: " + employee2.CalculatePay());

    }

}

/*

    Output:

    Employee4 Alice earned: 1500

    Employee4 Bob earned: 1200

*/

巴特西

override 修饰符

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