C#线程同步ReaderWriterLockSlim

ReaderWriterLockSlim可以将读锁和写锁进行分离，读锁允许多线程读取数据，写锁在被释放前会阻塞了其他线程的所有操作。下面以一个读Dictionary数据作为示例

 static ReaderWriterLockSlim _rw = new ReaderWriterLockSlim();
        static Dictionary<int, int> _items = new Dictionary<int, int>();
        static void Read()
        {
            
            Console.WriteLine("Reading contents of a dictionary");
            while (true)
            {
                try
                {
                    _rw.EnterReadLock();
                    foreach(var key in _items.Keys)
                    {
                        Console.WriteLine("读内容：{0}---{1}", key,Thread.CurrentThread.Name);
                        Thread.Sleep(TimeSpan.FromSeconds(0.1));
                    }
                }
                finally
                {
              
                    _rw.ExitReadLock();
                }
            }
        }
        static void Write(string threadName)
        {
            while (true)
            {
                try
                {
                    int newKey = new Random().Next(250);
                    _rw.EnterUpgradeableReadLock();
                    if (!_items.ContainsKey(newKey))
                    {
                        try
                        {
                            _rw.EnterWriteLock();
                            _items[newKey] = 1;
                            Console.WriteLine("Now key {0} is added to a dictionary by a {1}", newKey, threadName) ;
                        }
                        finally
                        {
                            _rw.ExitWriteLock();
                        }
                        Thread.Sleep(TimeSpan.FromSeconds(0.1));
                    }
                }
                finally
                {
                    _rw.ExitUpgradeableReadLock();
                }
            }
        }
         static void Main(string[] args)
        {
            new Thread(Read) { IsBackground = true }.Start();
            new Thread(Read) { IsBackground = true }.Start()；
            new Thread(() => Write("Thread 1")) { IsBackground = true }.Start();
           Thread.Sleep(TimeSpan.FromSeconds(30));
        }

上图是运行后的结果，截取了部分，可以看到可以支持多个读锁和单个写锁。

_rw.EnterReadLock()获取读锁_rw.EnterUpgradeableReadLock()获取写锁