Theoverride modifier is required to extend or modify the abstract or virtual implementation of an inherited method, property, indexer, or event.

In the following example, theSquare class must provide an overridden implementation ofGetArea becauseGetArea is inherited from the abstractShape class:

abstract class Shape{    public abstract int GetArea();}class Square : Shape{    private int _side;    public Square(int n) => _side = n;    // GetArea method is required to avoid a compile-time error.    public override int GetArea() => _side * _side;    static void Main()    {        var sq = new Square(12);        Console.WriteLine($"Area of the square = {sq.GetArea()}");    }}// Output: Area of the square = 144

Anoverride method provides a new implementation of the method inherited from a base class. The method that is overridden by anoverride declaration is known as the overridden base method. Anoverride method must have the same signature as the overridden base method.override methods support covariant return types. In particular, the return type of anoverride method can derive from the return type of the corresponding base method.

You cannot override a non-virtual or static method. The overridden base method must bevirtual,abstract, oroverride.

Anoverride declaration cannot change the accessibility of thevirtual method. Both theoverride method and thevirtual method must have the sameaccess level modifier.

You cannot use thenew,static, orvirtual modifiers to modify anoverride method.

An overriding property declaration must specify exactly the same access modifier, type, and name as the inherited property. Read-only overriding properties support covariant return types. The overridden property must bevirtual,abstract, oroverride.

For more information about how to use theoverride keyword, seeVersioning with the Override and New Keywords andKnowing when to use Override and New Keywords. For information about inheritance, seeInheritance.

Example

This example defines a base class namedEmployee, and a derived class namedSalesEmployee. TheSalesEmployee class includes an extra field,salesbonus, and overrides the methodCalculatePay in order to take it into account.

class TestOverride{    public class Employee    {        public string Name { get; }        // Basepay is defined as protected, so that it may be        // accessed only by this class and derived classes.        protected decimal _basepay;        // Constructor to set the name and basepay values.        public Employee(string name, decimal basepay)        {            Name = name;            _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)        {            _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.        var employee1 = new SalesEmployee("Alice", 1000, 500);        var employee2 = new Employee("Bob", 1200);        Console.WriteLine($"Employee1 {employee1.Name} earned: {employee1.CalculatePay()}");        Console.WriteLine($"Employee2 {employee2.Name} earned: {employee2.CalculatePay()}");    }}/*    Output:    Employee1 Alice earned: 1500    Employee2 Bob earned: 1200*/

C# language specification

For more information, see theOverride methods section of theC# language specification.

For more information about covariant return types, see thefeature proposal note.

See also

• Inheritance
• C# keywords
• Modifiers
• abstract
• virtual
• new (modifier)
• Polymorphism