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  • C#中的volatile关键字

    volatile 关键字指示一个字段可以由多个同时执行的线程修改。 声明为 volatile 的字段不受编译器优化(假定由单个线程访问)的限制。 这样可以确保该字段在任何时间呈现的都是最新的值。

    volatile 修饰符通常用于由多个线程访问、但不使用 lock 语句对访问进行序列化的字段。

    volatile 关键字可应用于以下类型的字段:

    • 引用类型。

    • 指针类型(在不安全的上下文中)。 请注意,虽然指针本身可以是可变的,但是它指向的对象不能是可变的。 换句话说,不能声明“指向可变对象的指针”。

    • 类型,如 sbyte、byte、short、ushort、int、uint、char、float 和 bool。

    • 具有以下基类型之一的枚举类型:byte、sbyte、short、ushort、int 或 uint。

    • 已知为引用类型的泛型类型参数。

    • IntPtr 和 UIntPtr

    可变关键字仅可应用于类或结构的字段。 不能将局部变量声明为 volatile

    示例

    下面的示例说明如何将公共字段变量声明为 volatile

    class VolatileTest
    {
        public volatile int i;
    
        public void Test(int _i)
        {
            i = _i;
        }
    }

    示例

    下面的示例演示如何创建辅助线程,并用它与主线程并行执行处理。 有关多线程处理的背景信息,请参阅 线程线程

    using System;
    using System.Threading;
    
    public class Worker
    {
        // This method is called when the thread is started.
        public void DoWork()
        {
            while (!_shouldStop)
            {
                Console.WriteLine("Worker thread: working...");
            }
            Console.WriteLine("Worker thread: terminating gracefully.");
        }
        public void RequestStop()
        {
            _shouldStop = true;
        }
        // Keyword volatile is used as a hint to the compiler that this data
        // member is accessed by multiple threads.
        private volatile bool _shouldStop;
    }
    
    public class WorkerThreadExample
    {
        static void Main()
        {
            // Create the worker thread object. This does not start the thread.
            Worker workerObject = new Worker();
            Thread workerThread = new Thread(workerObject.DoWork);
    
            // Start the worker thread.
            workerThread.Start();
            Console.WriteLine("Main thread: starting worker thread...");
    
            // Loop until the worker thread activates.
            while (!workerThread.IsAlive) ;
    
            // Put the main thread to sleep for 1 millisecond to
            // allow the worker thread to do some work.
            Thread.Sleep(1);
    
            // Request that the worker thread stop itself.
            workerObject.RequestStop();
    
            // Use the Thread.Join method to block the current thread 
            // until the object's thread terminates.
            workerThread.Join();
            Console.WriteLine("Main thread: worker thread has terminated.");
        }
        // Sample output:
        // Main thread: starting worker thread...
        // Worker thread: working...
        // Worker thread: working...
        // Worker thread: working...
        // Worker thread: working...
        // Worker thread: working...
        // Worker thread: working...
        // Worker thread: terminating gracefully.
        // Main thread: worker thread has terminated.
    }
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  • 原文地址:https://www.cnblogs.com/bincoding/p/8365713.html
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