应用程序中的所有线程都可以访问方法中的公用字段。要同步对公用字段的访问，您可以使用属性替代字段，并使用 ReaderWriterLock 对象控制访问。为此，请按照下列步骤操作：

using System;
using System.Threading;

namespace MultiThreadApplication
{
    class Class1
    {
        private ReaderWriterLock rwl = new ReaderWriterLock();
        private long myNumber;
        public long Number   // the Number property
        {
            get
            {
                //Acquire a read lock on the resource.
                rwl.AcquireReaderLock(Timeout.Infinite);
                try
                {
                    Console.WriteLine("Thread:{0} starts getting the Number", Thread.CurrentThread.GetHashCode());
                    Thread.Sleep(50);
                    Console.WriteLine("Thread:{0} got the Number", Thread.CurrentThread.GetHashCode());

                }
                finally
                {
                    //Release the lock.
                    rwl.ReleaseReaderLock();
                }
                return myNumber;
            }
            set
            {
                //Acquire a write lock on the resource.
                rwl.AcquireWriterLock(Timeout.Infinite);
                try
                {
                    Console.WriteLine("Thread: {0} start writing the Number", Thread.CurrentThread.GetHashCode());
                    Thread.Sleep(50);
                    myNumber = value;
                    Console.WriteLine("Thread: {0} written the Number", Thread.CurrentThread.GetHashCode());
                }
                finally
                {
                    //Release the lock.
                    rwl.ReleaseWriterLock();
                }
            }
        }

        [STAThread]
        static void Main(string[] args)
        {
            Thread[] threadArray = new Thread[20];
            int threadNum;


            Class1 Myclass = new Class1();
            ThreadStart myThreadStart = new ThreadStart(Myclass.AccessGlobalResource);

            //Create 20 threads.
            for (threadNum = 0; threadNum < 20; threadNum++)
            {
                threadArray[threadNum] = new Thread(myThreadStart);
            }

            //Start the threads.
            for (threadNum = 0; threadNum < 20; threadNum++)
            {
                threadArray[threadNum].Start();
            }

            //Wait until all the thread spawn out finish.
            for (threadNum = 0; threadNum < 20; threadNum++)
                threadArray[threadNum].Join();

            Console.WriteLine("All operations have completed. Press enter to exit");
            Console.ReadLine();
        }

        public void AccessGlobalResource()
        {
            Random rnd = new Random();
            long theNumber;

            if (rnd.Next() % 2 != 0)
                theNumber = Number;
            else
            {
                theNumber = rnd.Next();
                Number = theNumber;
            }

        }
    }
}

说明了读写共享资源访问是不冲图的，如下图所示（这个方式解决了多个线程可同时读，只有一个线程可以定的操作的协调）