看一下以下兩個例子的運行結果：
//testthread.cs
using system;using system.threading;public class test{    static int count=0;        static void main()    {        threadstart job = new threadstart(threadjob);        thread thread = new thread(job);        thread.start();                for (int i=0; i < 5; i++)        {            count++;        }                thread.join();        console.writeline ("final count: {0}", count);    }        static void threadjob()    {        for (int i=0; i < 5; i++)        {            count++;        }    }}    

//innerdatathread.cs

using system;using system.threading;public class test{    static int count=0;        static void main()    {        threadstart job = new threadstart(threadjob);        thread thread = new thread(job);        thread.start();                for (int i=0; i < 5; i++)        {            int tmp = count;            console.writeline ("read count={0}", tmp);            thread.sleep(50);            tmp++;            console.writeline ("incremented tmp to {0}", tmp);            thread.sleep(20);            count = tmp;            console.writeline ("written count={0}", tmp);            thread.sleep(30);        }                thread.join();        console.writeline ("final count: {0}", count);    }        static void threadjob()    {        for (int i=0; i < 5; i++)        {            int tmp = count;            console.writeline ("/t/t/t/tread count={0}", tmp);            thread.sleep(20);            tmp++;            console.writeline ("/t/t/t/tincremented tmp to {0}", tmp);            thread.sleep(10);            count = tmp;            console.writeline ("/t/t/t/twritten count={0}", tmp);            thread.sleep(40);        }    }}
read count=0                                read count=0                                incremented tmp to 1                                written count=1incremented tmp to 1written count=1                                read count=1                                incremented tmp to 2read count=1                                written count=2                                read count=2incremented tmp to 2                                incremented tmp to 3written count=2                                written count=3read count=3                                read count=3incremented tmp to 4                                incremented tmp to 4                                written count=4written count=4                                read count=4read count=4                                incremented tmp to 5                                written count=5incremented tmp to 5written count=5read count=5incremented tmp to 6written count=6final count: 6

再比較下面這個例子：

//使用monitor.enter/exit
//monitorthread.cs

using system;
using system.threading;

public class test
{
    static int count=0;
    static readonly object countlock = new object();
   
    static void main()
    {
        threadstart job = new threadstart(threadjob);
        thread thread = new thread(job);
        thread.start();
       
        for (int i=0; i < 5; i++)
        {
            monitor.enter(countlock);
            int tmp = count;
            console.writeline ("read count={0}", tmp);
            thread.sleep(50);
            tmp++;
            console.writeline ("incremented tmp to {0}", tmp);
            thread.sleep(20);
            count = tmp;
            console.writeline ("written count={0}", tmp);
            monitor.exit(countlock);
            thread.sleep(30);
        }
       
        thread.join();
        console.writeline ("final count: {0}", count);
    }
   
    static void threadjob()
    {
        for (int i=0; i < 5; i++)
        {
            monitor.enter(countlock);
            int tmp = count;
            console.writeline ("/t/t/t/tread count={0}", tmp);
            thread.sleep(20);
            tmp++;
            console.writeline ("/t/t/t/tincremented tmp to {0}", tmp);
            thread.sleep(10);
            count = tmp;
            console.writeline ("/t/t/t/twritten count={0}", tmp);
            monitor.exit(countlock);
            thread.sleep(40);
        }
    }
}

結果與上例innerdatathread.cs是不一樣的，原因就在于monitor的使用了。

read count=0incremented tmp to 1written count=1                                read count=1                                incremented tmp to 2                                written count=2read count=2incremented tmp to 3written count=3                                read count=3                                incremented tmp to 4                                written count=4read count=4incremented tmp to 5written count=5                                read count=5                                incremented tmp to 6                                written count=6read count=6incremented tmp to 7written count=7                                read count=7                                incremented tmp to 8                                written count=8read count=8incremented tmp to 9written count=9                                read count=9                                incremented tmp to 10                                written count=10final count: 10

下面使用lock來鎖定線程：
// lockthread.cs
using system;
using system.threading;

public class test
{
    static int count=0;
    static readonly object countlock = new object();
   
    static void main()
    {
        threadstart job = new threadstart(threadjob);
        thread thread = new thread(job);
        thread.start();
       
        for (int i=0; i < 5; i++)
        {
            lock (countlock)
            {
                int tmp = count;
                console.writeline ("read count={0}", tmp);
                thread.sleep(50);
                tmp++;
                console.writeline ("incremented tmp to {0}", tmp);
                thread.sleep(20);
                count = tmp;
                console.writeline ("written count={0}", tmp);
            }
            thread.sleep(30);
        }
       
        thread.join();
        console.writeline ("final count: {0}", count);
    }
   
    static void threadjob()
    {
        for (int i=0; i < 5; i++)
        {
            lock (countlock)
            {
                int tmp = count;
                console.writeline ("/t/t/t/tread count={0}", tmp);
                thread.sleep(20);
                tmp++;
                console.writeline ("/t/t/t/tincremented tmp to {0}", tmp);
                if (count < 100)
                    throw new exception();
                thread.sleep(10);
                count = tmp;
                console.writeline ("/t/t/t/twritten count={0}", tmp);
            }
            thread.sleep(40);
        }
    }
}

結果如何？與monitorthread.cs比較一下，再想想看。