C#线程中LOCK的意义

学习心得，为的是让新人能理解，高手直接绕~

lock 确保当一个线程位于代码的临界区时，另一个线程不进入临界区。如果其他线程试图进入锁定的代码，则它将一直等待（即被阻止），直到该对象被释放。

引用一句看到的资料里比较流行的话“前面说过，每个线程都有自己的资源，但是代码区是共享的，即每个线程都可以执行相同的函数。这可能带来的问题就是几个线程同时执行一个函数，导致数据的混乱，产生不可预料的结果，因此我们必须避免这种情况的发生。”

建一个控制台应用程序

首先引用这个.....

using System.Threading;

    class ThreadInterrupt
    {
        static void Main()
        {
            test tt = new test();
            ///写这么多个为的是让环境更加容易创造出氛围来，线程多起来，出问题的可能性就大
            new Thread(new ThreadStart(tt.test1)).Start();
            new Thread(new ThreadStart(tt.test1)).Start();
            new Thread(new ThreadStart(tt.test1)).Start();
            new Thread(new ThreadStart(tt.test1)).Start();
            new Thread(new ThreadStart(tt.test1)).Start();
            new Thread(new ThreadStart(tt.test1)).Start();
            new Thread(new ThreadStart(tt.test1)).Start();
            new Thread(new ThreadStart(tt.test1)).Start();
            new Thread(new ThreadStart(tt.test1)).Start();
            new Thread(new ThreadStart(tt.test1)).Start();
            new Thread(new ThreadStart(tt.test1)).Start();
            new Thread(new ThreadStart(tt.test1)).Start();
            new Thread(new ThreadStart(tt.test1)).Start();
            new Thread(new ThreadStart(tt.test1)).Start();
            new Thread(new ThreadStart(tt.test1)).Start();
            new Thread(new ThreadStart(tt.test1)).Start();
            new Thread(new ThreadStart(tt.test1)).Start();
            new Thread(new ThreadStart(tt.test1)).Start();
            new Thread(new ThreadStart(tt.test1)).Start();
            new Thread(new ThreadStart(tt.test1)).Start();
            new Thread(new ThreadStart(tt.test1)).Start();
            new Thread(new ThreadStart(tt.test1)).Start();
            new Thread(new ThreadStart(tt.test1)).Start();
            new Thread(new ThreadStart(tt.test1)).Start();
            new Thread(new ThreadStart(tt.test1)).Start();
            new Thread(new ThreadStart(tt.test1)).Start();
            new Thread(new ThreadStart(tt.test1)).Start();
            new Thread(new ThreadStart(tt.test1)).Start();


            
        }
        class test
        {
            private int  a;
            private object b;
            public test()
            {
                a = 8;
                b = new object();
            }

            public void test1()
            {


                //////在该位置加lock(this){
          
                ///没有lock的情况下，所有线程都会实时进入(线程是无序的)
                    Console.WriteLine("the thread:{0} 进入 ...", Thread.CurrentThread.GetHashCode());
                /////然后每个线程都会去判断a的值
                    if (a == 0)
                    {
                        Console.WriteLine("a={0},b={1},当前进程{2}", a, b, Thread.CurrentThread.GetHashCode());
                        return;
                    }
                ///到此，如果线程哈希值不是4，则休眠一秒钟，为的是让晚于线程4但是已经判断a！=0的线程再次停留，给线程4充分的事件去把a置为0
                    if (Thread.CurrentThread.GetHashCode() != 4)
                    {
                        Thread.Sleep(1000);
                    }
                /////用当前线程的哈希值除a，为的是如果a为0的话能出现异常，当然可以随便写 110/a,907867869/a都可以
                    b = (Thread.CurrentThread.GetHashCode() / a).ToString();
                ///每个线程进入时对a做一些改变，无关紧要的
                    a -= Thread.CurrentThread.GetHashCode();
                    ///如果线程哈希值是4，则将a置为0。
                    if (Thread.CurrentThread.GetHashCode() == 4)
                    {
                        a = 0;
                    }

                    Console.WriteLine("a={0},b={1},当前进程{2}", a, b, Thread.CurrentThread.GetHashCode());
                
                //////lock的 "}"
            }
         
        }

    }