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C#: this

使用手冊C# · 實用指南

表示目前實例、此類別的建構子、索引器或擴展方法參數。

簡單範例 (Example.cs)

請將此範例另存為 Example.cs，並與本頁其他範例分開執行。

Example.cs:

// PROJECT-EXAMPLE
System.Console.WriteLine(new Item(7).Count);
class Item
{
    public int Count;
    public Item(int count) { this.Count = count; }
}

結果:

7

句法

this.field / Constructor() : this(...) / this[int index]

例1：基本形式

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;
}

例2：另一種實用形式

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;
}

官方來源：Microsoft學習。