EN CSharp Keyword override

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C#: override

Handbook C# · Practical Guide

Replaces an inherited virtual or abstract implementation. Calls through the base type remain polymorphic.

Simple example (Example.cs)

Save this example separately as Example.cs. Run it independently of the other examples on this page.

Example.cs:

// PROJECT-EXAMPLE
Animal animal = new Dog();
System.Console.WriteLine(animal.Sound());
class Animal { public virtual string Sound() => "?"; }
class Dog : Animal { public override string Sound() => "Woof"; }

Result:

Woof

Syntax

public override ReturnType Method(...) { ... }

Example 1: simple form

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using System.IO;
using System.Runtime.InteropServices;
using System.Runtime.CompilerServices;

public static class Program
{
    public static async Task Main(string[] args)
    {
        Entity entity = new Player("Archer");
        Console.WriteLine(entity.Describe());
        Console.WriteLine(entity.Code);
    }
}
public interface ILabel { string Label { get; } }
public abstract class Entity : ILabel
{
    private readonly string name;
    protected Entity(string name) { this.name = name; }
    protected string Name => name;
    internal int Code { get; set; } = 7;
    public virtual string Label => Name;
    public abstract string Describe();
}
public sealed class Player : Entity
{
    public Player(string name) : base(name) { }
    public override string Label => "Player: " + base.Label;
    public override string Describe() => Label;
}

Example 2: another practical form

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using System.IO;
using System.Runtime.InteropServices;
using System.Runtime.CompilerServices;

public static class Program
{
    public static async Task Main(string[] args)
    {
        NamedCounter value = new();
        Console.WriteLine(value.Describe());
        Counter parent = value;
        Console.WriteLine(parent.Describe());
    }
}
public interface ICounter { int Count { get; } }
public class Counter : ICounter
{
    private int count;
    public Counter() : this(1) { }
    public Counter(int count) { this.count = count; }
    public int Count => count;
    protected internal virtual string Format() => count.ToString();
    public string Describe() => Format();
}
public sealed class NamedCounter : Counter
{
    public NamedCounter() : base(4) { }
    public new string Describe() => "Named: " + base.Describe();
    protected internal override string Format() => "Count=" + Count;
}

Official source: Microsoft Learn.