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。
C#
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
*/