DE CSharp Keyword virtual

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C#: virtual

Handbuch C# · Praktischer Leitfaden

Ermöglicht einem Nachkommen, eine Methode oder Eigenschaft per Override zu überschreiben.

Einfaches Beispiel (Example.cs)

Speichern Sie dieses Beispiel separat als Example.cs. Führen Sie es unabhängig von den anderen Beispielen dieser Seite aus.

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"; }

Ergebnis:

Woof

Syntax

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

Beispiel 1: Grundform

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;
}

Beispiel 2: eine weitere praktische 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;
}

Offizielle Quelle: Microsoft Learn.