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C#: volatile

使用手冊C# · 實用指南

定義線程間字段的讀寫可見性規則。不會使像 counter++ 這樣的複合操作原子化。

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 State().Stopped);
class State { public volatile bool Stopped = false; }

結果:

False

句法

private volatile bool stopping;

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)
    {
        Worker worker = new();
        await Task.Run(() => worker.Stopping = true);
        Console.WriteLine(worker.Stopping);
    }
}
public sealed class Worker { public volatile bool Stopping; }

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)
    {
        State state = new();
        state.Publish();
        Console.WriteLine(state.IsReady);
    }
}
public sealed class State { private volatile bool ready; public bool IsReady => ready; public void Publish() { ready = true; } }

官方來源：Microsoft學習。