C#线程安全类型

1、IProducerConsumerCollection (线程安全接口)
　　此接口的所有实现必须都启用此接口的所有成员，若要从多个线程同时使用。

using System;
using System.Collections;
using System.Collections.Concurrent;
using System.Collections.Generic;

namespace ConsoleApp1
{
    public class SafeStack<T> : IProducerConsumerCollection<T>
    {
        // Used for enforcing thread-safety
        private object m_lockObject = new object();

        // We'll use a regular old Stack for our core operations
        private Stack<T> m_sequentialStack = null;

        //
        // Constructors
        //
        public SafeStack()
        {
            m_sequentialStack = new Stack<T>();
        }

        public SafeStack(IEnumerable<T> collection)
        {
            m_sequentialStack = new Stack<T>(collection);
        }

        //
        // Safe Push/Pop support
        //
        public void Push(T item)
        {
            lock (m_lockObject) m_sequentialStack.Push(item);
        }

        public bool TryPop(out T item)
        {
            bool rval = true;
            lock (m_lockObject)
            {
                if (m_sequentialStack.Count == ) { item = default(T); rval = false; }
                else item = m_sequentialStack.Pop();
            }
            return rval;
        }

        //
        // IProducerConsumerCollection(T) support
        //
        public bool TryTake(out T item)
        {
            return TryPop(out item);
        }

        public bool TryAdd(T item)
        {
            Push(item);
            return true; // Push doesn't fail
        }

        public T[] ToArray()
        {
            T[] rval = null;
            lock (m_lockObject) rval = m_sequentialStack.ToArray();
            return rval;
        }

        public void CopyTo(T[] array, int index)
        {
            lock (m_lockObject) m_sequentialStack.CopyTo(array, index);
        }

        //
        // Support for IEnumerable(T)
        //
        public IEnumerator<T> GetEnumerator()
        {
            // The performance here will be unfortunate for large stacks,
            // but thread-safety is effectively implemented.
            Stack<T> stackCopy = null;
            lock (m_lockObject) stackCopy = new Stack<T>(m_sequentialStack);
            return stackCopy.GetEnumerator();
        }

        //
        // Support for IEnumerable
        //
        IEnumerator IEnumerable.GetEnumerator()
        {
            return ((IEnumerable<T>)this).GetEnumerator();
        }

        //
        // Support for ICollection
        //
        public bool IsSynchronized
        {
            get { return true; }
        }

        public object SyncRoot
        {
            get { return m_lockObject; }
        }

        public int Count
        {
            get { return m_sequentialStack.Count; }
        }

        public void CopyTo(Array array, int index)
        {
            lock (m_lockObject) ((ICollection)m_sequentialStack).CopyTo(array, index);
        }
    }
}

SafeStack

using System;
using System.Collections.Concurrent;

namespace ConsoleApp1
{
    class Program
    {
        static void Main()
        {
            TestSafeStack();

            // Keep the console window open in debug mode.
            Console.WriteLine("Press any key to exit.");
            Console.ReadKey();
        }

        // Test our implementation of IProducerConsumerCollection(T)
        // Demonstrates:
        //      IPCC(T).TryAdd()
        //      IPCC(T).TryTake()
        //      IPCC(T).CopyTo()
        static void TestSafeStack()
        {
            SafeStack<int> stack = new SafeStack<int>();
            IProducerConsumerCollection<int> ipcc = (IProducerConsumerCollection<int>)stack;

            // Test Push()/TryAdd()
            stack.Push(); Console.WriteLine("Pushed 10");
            ipcc.TryAdd(); Console.WriteLine("IPCC.TryAdded 20");
            stack.Push(); Console.WriteLine("Pushed 15");

            int[] testArray = new int[];

            // Try CopyTo() within boundaries
            try
            {
                ipcc.CopyTo(testArray, );
                Console.WriteLine("CopyTo() within boundaries worked, as expected");
            }
            catch (Exception e)
            {
                Console.WriteLine("CopyTo() within boundaries unexpectedly threw an exception: {0}", e.Message);
            }

            // Try CopyTo() that overflows
            try
            {
                ipcc.CopyTo(testArray, );
                Console.WriteLine("CopyTo() with index overflow worked, and it SHOULD NOT HAVE");
            }
            catch (Exception e)
            {
                Console.WriteLine("CopyTo() with index overflow threw an exception, as expected: {0}", e.Message);
            }

            // Test enumeration
            Console.Write("Enumeration (should be three items): ");
            foreach (int item in stack)
                Console.Write("{0} ", item);
            Console.WriteLine("");

            // Test TryPop()
            int popped = ;
            if (stack.TryPop(out popped))
            {
                Console.WriteLine("Successfully popped {0}", popped);
            }
            else Console.WriteLine("FAILED to pop!!");

            // Test Count
            Console.WriteLine("stack count is {0}, should be 2", stack.Count);

            // Test TryTake()
            if (ipcc.TryTake(out popped))
            {
                Console.WriteLine("Successfully IPCC-TryTaked {0}", popped);
            }
            else Console.WriteLine("FAILED to IPCC.TryTake!!");
        }
    }
}

Program

2、ConcurrentStack类:安全堆栈

using System;
using System.Collections.Concurrent;
using System.Threading;
using System.Threading.Tasks;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            Task t = RunProgram();
            t.Wait();
        }

        static async Task RunProgram()
        {
            var taskStack = new ConcurrentStack<CustomTask>();
            var cts = new CancellationTokenSource();

            var taskSource = Task.Run(() => TaskProducer(taskStack));

            Task[] processors = new Task[];
            for (int i = ; i <= ; i++)
            {
                string processorId = i.ToString();
                processors[i - ] = Task.Run(
                    () => TaskProcessor(taskStack, "Processor " + processorId, cts.Token));
            }

            await taskSource;
            cts.CancelAfter(TimeSpan.FromSeconds());

            await Task.WhenAll(processors);
        }

        static async Task TaskProducer(ConcurrentStack<CustomTask> stack)
        {
            for (int i = ; i <= ; i++)
            {
                await Task.Delay();
                var workItem = new CustomTask { Id = i };
                stack.Push(workItem);
                Console.WriteLine("Task {0} has been posted", workItem.Id);
            }
        }

        static async Task TaskProcessor(
            ConcurrentStack<CustomTask> stack, string name, CancellationToken token)
        {
            await GetRandomDelay();
            do
            {
                CustomTask workItem;
                bool popSuccesful = stack.TryPop(out workItem);
                if (popSuccesful)
                {
                    Console.WriteLine("Task {0} has been processed by {1}", workItem.Id, name);
                }

                await GetRandomDelay();
            }
            while (!token.IsCancellationRequested);
        }

        static Task GetRandomDelay()
        {
            int delay = new Random(DateTime.Now.Millisecond).Next(, );
            return Task.Delay(delay);
        }

        class CustomTask
        {
            public int Id { get; set; }
        }
    }
}

Program

3、ConcurrentQueue类:安全队列

using System;
using System.Collections.Concurrent;
using System.Threading;
using System.Threading.Tasks;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            Task t = RunProgram();
            t.Wait();
        }

        static async Task RunProgram()
        {
            var taskQueue = new ConcurrentQueue<CustomTask>();
            var cts = new CancellationTokenSource();

            var taskSource = Task.Run(() => TaskProducer(taskQueue));

            Task[] processors = new Task[];
            for (int i = ; i <= ; i++)
            {
                string processorId = i.ToString();
                processors[i - ] = Task.Run(
                    () => TaskProcessor(taskQueue, "Processor " + processorId, cts.Token));
            }

            await taskSource;
            cts.CancelAfter(TimeSpan.FromSeconds());

            await Task.WhenAll(processors);
        }

        static async Task TaskProducer(ConcurrentQueue<CustomTask> queue)
        {
            for (int i = ; i <= ; i++)
            {
                await Task.Delay();
                var workItem = new CustomTask { Id = i };
                queue.Enqueue(workItem);
                Console.WriteLine("插入Task {0} has been posted ThreadID={1}", workItem.Id, Thread.CurrentThread.ManagedThreadId);
            }
        }

        static async Task TaskProcessor(
            ConcurrentQueue<CustomTask> queue, string name, CancellationToken token)
        {
            CustomTask workItem;
            bool dequeueSuccesful = false;

            await GetRandomDelay();
            do
            {
                dequeueSuccesful = queue.TryDequeue(out workItem);
                if (dequeueSuccesful)
                {
                    Console.WriteLine("读取Task {0} has been processed by {1} ThreadID={2}",
                                        workItem.Id, name, Thread.CurrentThread.ManagedThreadId);
                }

                await GetRandomDelay();
            }
            while (!token.IsCancellationRequested);
        }

        static Task GetRandomDelay()
        {
            int delay = new Random(DateTime.Now.Millisecond).Next(, );
            return Task.Delay(delay);
        }

        class CustomTask
        {
            public int Id { get; set; }
        }
    }
}

Program

4、ConcurrentDictionary类
　　ConcurrentDictionary类写操作比使用锁的通常字典(Dictionary)要慢的多,而读操作则要快些。因此对字典要大量的线程安全的读操作,ConcurrentDictionary类是最好的选择
　　ConcurrentDictionary类的实现使用了细粒度锁(fine-grained locking)技术,这在多线程写入方面比使用锁的通常的字典(也被称为粗粒度锁)

using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Diagnostics;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            var concurrentDictionary = new ConcurrentDictionary<int, string>();
            var dictionary = new Dictionary<int, string>();

            var sw = new Stopwatch();

            sw.Start();
            for (int i = ; i < ; i++)
            {
                lock (dictionary)
                {
                    dictionary[i] = Item;
                }
            }
            sw.Stop();
            Console.WriteLine("Writing to dictionary with a lock: {0}", sw.Elapsed);

            sw.Restart();
            for (int i = ; i < ; i++)
            {
                concurrentDictionary[i] = Item;
            }
            sw.Stop();
            Console.WriteLine("Writing to a concurrent dictionary: {0}", sw.Elapsed);

            sw.Restart();
            for (int i = ; i < ; i++)
            {
                lock (dictionary)
                {
                    CurrentItem = dictionary[i];
                }
            }
            sw.Stop();
            Console.WriteLine("Reading from dictionary with a lock: {0}", sw.Elapsed);

            sw.Restart();
            for (int i = ; i < ; i++)
            {
                CurrentItem = concurrentDictionary[i];
            }
            sw.Stop();
            Console.WriteLine("Reading from a concurrent dictionary: {0}", sw.Elapsed);
        }

        const string Item = "Dictionary item";
        public static string CurrentItem;
    }
}

Program

5、ConcurrentBag类

namespace ConsoleApp1
{
    class CrawlingTask
    {
        public string UrlToCrawl { get; set; }

        public string ProducerName { get; set; }
    }
}

CrawlingTask

using System.Collections.Generic;

namespace ConsoleApp1
{
    static class Module
    {
        public static Dictionary<string, string[]> _contentEmulation = new Dictionary<string, string[]>();

        public static void CreateLinks()
        {
            _contentEmulation["http://microsoft.com/"] = new[] { "http://microsoft.com/a.html", "http://microsoft.com/b.html" };
            _contentEmulation["http://microsoft.com/a.html"] = new[] { "http://microsoft.com/c.html", "http://microsoft.com/d.html" };
            _contentEmulation["http://microsoft.com/b.html"] = new[] { "http://microsoft.com/e.html" };

            _contentEmulation["http://google.com/"] = new[] { "http://google.com/a.html", "http://google.com/b.html" };
            _contentEmulation["http://google.com/a.html"] = new[] { "http://google.com/c.html", "http://google.com/d.html" };
            _contentEmulation["http://google.com/b.html"] = new[] { "http://google.com/e.html", "http://google.com/f.html" };
            _contentEmulation["http://google.com/c.html"] = new[] { "http://google.com/h.html", "http://google.com/i.html" };

            _contentEmulation["http://facebook.com/"] = new[] { "http://facebook.com/a.html", "http://facebook.com/b.html" };
            _contentEmulation["http://facebook.com/a.html"] = new[] { "http://facebook.com/c.html", "http://facebook.com/d.html" };
            _contentEmulation["http://facebook.com/b.html"] = new[] { "http://facebook.com/e.html" };

            _contentEmulation["http://twitter.com/"] = new[] { "http://twitter.com/a.html", "http://twitter.com/b.html" };
            _contentEmulation["http://twitter.com/a.html"] = new[] { "http://twitter.com/c.html", "http://twitter.com/d.html" };
            _contentEmulation["http://twitter.com/b.html"] = new[] { "http://twitter.com/e.html" };
            _contentEmulation["http://twitter.com/c.html"] = new[] { "http://twitter.com/f.html", "http://twitter.com/g.html" };
            _contentEmulation["http://twitter.com/d.html"] = new[] { "http://twitter.com/h.html" };
            _contentEmulation["http://twitter.com/e.html"] = new[] { "http://twitter.com/i.html" };
        }
    }
}

Module

using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Threading.Tasks;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            Module.CreateLinks();
            Task t = RunProgram();
            t.Wait();
        }

        static async Task RunProgram()
        {
            var bag = new ConcurrentBag<CrawlingTask>();

            string[] urls = new[] { "http://microsoft.com/", "http://google.com/", "http://facebook.com/", "http://twitter.com/" };

            var crawlers = new Task[];
            for (int i = ; i <= ; i++)
            {
                string crawlerName = "Crawler " + i.ToString();
                bag.Add(new CrawlingTask { UrlToCrawl = urls[i - ], ProducerName = "root" });
                crawlers[i - ] = Task.Run(() => Crawl(bag, crawlerName));
            }

            await Task.WhenAll(crawlers);
        }

        static async Task Crawl(ConcurrentBag<CrawlingTask> bag, string crawlerName)
        {
            CrawlingTask task;
            //尝试从bag中取出对象
            while (bag.TryTake(out task))
            {
                IEnumerable<string> urls = await GetLinksFromContent(task);
                if (urls != null)
                {
                    foreach (var url in urls)
                    {
                        var t = new CrawlingTask
                        {
                            UrlToCrawl = url,
                            ProducerName = crawlerName
                        };
                        //将子集插入到bag中
                        bag.Add(t);
                    }
                }
                Console.WriteLine("Indexing url {0} posted by {1} is completed by {2}!",
                    task.UrlToCrawl, task.ProducerName, crawlerName);
            }
        }

        static async Task<IEnumerable<string>> GetLinksFromContent(CrawlingTask task)
        {
            await GetRandomDelay();

            if (Module._contentEmulation.ContainsKey(task.UrlToCrawl)) return Module._contentEmulation[task.UrlToCrawl];

            return null;
        }

        static Task GetRandomDelay()
        {
            int delay = new Random(DateTime.Now.Millisecond).Next(, );
            return Task.Delay(delay);
        }

    }
}

Program

6、BlockingCollection类
　　BlockingCollection类: 我们能够改变任务存储在阻塞集合中的方式。默认情况下它使用的是ConcurrentQueue容器,但是我们能够使用任何实现了IProducerConsumerCollection泛型接口的集合。

namespace ConsoleApp1
{
    class CustomTask
    {
        public int Id { get; set; }
    }
}

CustomTask

using System;
using System.Threading.Tasks;

namespace ConsoleApp1
{
    static class Module
    {
        public static Task GetRandomDelay()
        {
            int delay = new Random(DateTime.Now.Millisecond).Next(, );
            return Task.Delay(delay);
        }
    }
}

Module

using System;
using System.Collections.Concurrent;
using System.Threading.Tasks;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Using a Queue inside of BlockingCollection");
            Console.WriteLine();
            Task t = RunProgram();
            t.Wait();

            //Console.WriteLine();
            //Console.WriteLine("Using a Stack inside of BlockingCollection");
            //Console.WriteLine();
            //Task t = RunProgram(new ConcurrentStack<CustomTask>());
            //t.Wait();
        }

        static async Task RunProgram(IProducerConsumerCollection<CustomTask> collection = null)
        {
            var taskCollection = new BlockingCollection<CustomTask>();
            if (collection != null)
                taskCollection = new BlockingCollection<CustomTask>(collection);
            //初始化collection中的数据
            var taskSource = Task.Run(() => TaskProducer(taskCollection));

            Task[] processors = new Task[];
            for (int i = ; i <= ; i++)
            {
                string processorId = "Processor " + i;
                processors[i - ] = Task.Run(
                    () => TaskProcessor(taskCollection, processorId));
            }

            await taskSource;

            await Task.WhenAll(processors);
        }
        /// <summary>
        /// 初始化collection中的数据
        /// </summary>
        /// <param name="collection"></param>
        /// <returns></returns>
        static async Task TaskProducer(BlockingCollection<CustomTask> collection)
        {
            for (int i = ; i <= ; i++)
            {
                await Task.Delay();
                var workItem = new CustomTask { Id = i };
                collection.Add(workItem);
                Console.WriteLine("Task {0} has been posted", workItem.Id);
            }
            collection.CompleteAdding();
        }
        /// <summary>
        /// 打印collection中的数据
        /// </summary>
        /// <param name="collection"></param>
        /// <param name="name"></param>
        /// <returns></returns>
        static async Task TaskProcessor(
            BlockingCollection<CustomTask> collection, string name)
        {
            await Module.GetRandomDelay();
            foreach (CustomTask item in collection.GetConsumingEnumerable())
            {
                Console.WriteLine("Task {0} has been processed by {1}", item.Id, name);
                await Module.GetRandomDelay();
            }
        }
    }
}

Program

7、使用ThreadStatic特性
　　ThreadStatic特性是最简单的TLS使用，且只支持静态字段，只需要在字段上标记这个特性就可以了

using System;
using System.Threading;

namespace ConsoleApp1
{
    class Program
    {
        //TLS中的str变量
        //可以看到，str静态字段在两个线程中都是独立存储的，互相不会被修改。
        [ThreadStatic]
        static string str = "hehe";

        static void Main(string[] args)
        {
            //另一个线程只会修改自己TLS中的hehe
            Thread th = new Thread(() => { str = "Mgen"; Display(); });
            th.Start();
            th.Join();
            Display();
        }
        static void Display()
        {
            Console.WriteLine("{0} {1}", Thread.CurrentThread.ManagedThreadId, str);
        }

    }
}

Program

8、使用命名的LocalDataStoreSlot类型
　　显然ThreadStatic特性只支持静态字段太受限制了。.NET线程类型中的LocalDataStoreSlot提供更好的TLS支持。我们先来看看命名的LocalDataStoreSlot类型，可以通过Thread.AllocateNamedDataSlot来分配一个命名的空间，通过Thread.FreeNamedDataSlot来销毁一个命名的空间。空间数据的获取和设置则通过Thread类型的GetData方法和SetData方法。

using System;
using System.Threading;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            //创建Slot
            LocalDataStoreSlot slot = Thread.AllocateNamedDataSlot("slot");

            //设置TLS中的值
            Thread.SetData(slot, "hehe");

            //修改TLS的线程
            Thread th = new Thread(() =>
            {
                Thread.SetData(slot, "Mgen");
                Display();
            });

            th.Start();
            th.Join();
            Display();

            //清除Slot
            Thread.FreeNamedDataSlot("slot");
        }

        //显示TLS中Slot值
        static void Display()
        {
            LocalDataStoreSlot dataslot = Thread.GetNamedDataSlot("slot");
            Console.WriteLine("{0} {1}", Thread.CurrentThread.ManagedThreadId, Thread.GetData(dataslot));
        }

    }
}

Program

9、使用未命名的LocalDataStoreSlot类型
　　线程同样支持未命名的LocalDataStoreSlot，未命名的LocalDataStoreSlot不需要手动清除，分配则需要Thread.AllocateDataSlot方法。注意由于未命名的LocalDataStoreSlot没有名称，因此无法使用Thread.GetNamedDataSlot方法，只能在多个线程中引用同一个LocalDataStoreSlot才可以对TLS空间进行操作，将上面的命名的LocalDataStoreSlot代码改成未命名的LocalDataStoreSlot执行

using System;
using System.Threading;

namespace ConsoleApp1
{
    class Program
    {
        //静态LocalDataStoreSlot变量
        static LocalDataStoreSlot slot;

        static void Main(string[] args)
        {
            //创建Slot
            slot = Thread.AllocateDataSlot();

            //设置TLS中的值
            Thread.SetData(slot, "hehe");

            //修改TLS的线程
            Thread th = new Thread(() =>
            {
                Thread.SetData(slot, "Mgen");
                Display();

            });

            th.Start();
            th.Join();
            Display();
        }

        //显示TLS中Slot值
        static void Display()
        {
            Console.WriteLine("{0} {1}", Thread.CurrentThread.ManagedThreadId, Thread.GetData(slot));
        }

    }
}

Program

10、使用.NET 4.0的ThreadLocal<T>类型
　　.NET 4.0在线程方面加入了很多东西，其中就包括ThreadLocal<T>类型，他的出现更大的简化了TLS的操作。ThreadLocal<T>类型和Lazy<T>惊人相似，构造函数参数是Func<T>用来创建对象（当然也可以理解成对象的默认值），然后用Value属性来得到或者设置这个对象。
　　ThreadLocal的操作或多或少有点像上面的未命名的LocalDataStoreSlot，但ThreadLocal感觉更简洁更好理解。

using System;
using System.Threading;

namespace ConsoleApp1
{
    class Program
    {
        static ThreadLocal<string> local;

        static void Main(string[] args)
        {
            //创建ThreadLocal并提供默认值
            local = new ThreadLocal<string>(() => "hehe");

            //修改TLS的线程
            Thread th = new Thread(() =>
            {

                local.Value = "Mgen";
                Display();
            });

            th.Start();
            th.Join();
            Display();
        }

        //显示TLS中数据值
        static void Display()
        {
            Console.WriteLine("{0} {1}", Thread.CurrentThread.ManagedThreadId, local.Value);
        }

    }
}

Program