c#中Monitor的使用

首先lock和Minitor有什么区别呢？
其实lock在IL代码中会被翻译成Monitor。也就是Monitor.Enter(obj)和Monitor.Exit(obj).
lock（obj）
{
}
等价为：
try
{    
      Monitor.Enter(obj)

}
catch（）
{}
finally
{
      Monitor.Exit(obj)

}
所以lock能做的，Monitor肯定能做，Monitor能做的，lock不一定能做。那么Monitor额外的功能呢？

1：Monitor.TryEnter(obj,timespan)----timeout之后，就不执行这段代码了。lock可是一直会死等的。
 
2：还有Monitor.Wait()和Monitor.Pulse()。在lock代码里面如果调用了Monitor.Wait()，会放弃对资源的所有权，让别的线程lock进来。然后别的线程代码里Pulse一下（让原线程进入到等待队列），然后在Wait一下释放资源，这样原线程的就可以继续执行了（代码还堵塞在wait那句话呢）。

也就是说，必须两个或多个线程共同调用Wait和Pulse，把资源的所有权抛来抛去，才不会死锁。

和AutoEvent相似是处理同步关系的，但是AutoEvent是跨进程的，而Monitor是针对线程的。
以下是MSDN的代码示例，调试起来很容易看出来两个函数的作用了，因为尽管是多线程程序，但是是同步操作，所以代码始终是单步执行的。

using System;
using System.Threading;
using System.Collections;

namespace MonitorCS1
{
    class
MonitorSample
    {
       
const int MAX_LOOP_TIME = 100;
       
Queue m_smplQueue;

public MonitorSample()
       
{
           
m_smplQueue = new Queue();
       
}
       
public void FirstThread()
       
{
           
int counter = 0;
           
lock (m_smplQueue)
           
{
               
while (counter < MAX_LOOP_TIME)
               
{
                   
//Wait, if the queue is busy.
                   
Monitor.Wait(m_smplQueue);
                   
//Push one element.
                   
m_smplQueue.Enqueue(counter);
                   
//Release the waiting thread.
                   
Monitor.Pulse(m_smplQueue);

counter++;
               
}
               
int i = 0;
           
}
       
}
       
public void SecondThread()
       
{
           
lock (m_smplQueue)
           
{
               
//Release the waiting thread.
               
Monitor.Pulse(m_smplQueue);
               
//Wait in the loop, while the queue is busy.
               
//Exit on the time-out when the first thread stops.
               
while (Monitor.Wait(m_smplQueue, 50000))
               
{
                   
//Pop the first element.
                   
int counter = (int)m_smplQueue.Dequeue();
                   
//Print the first element.
                   
Console.WriteLine(counter.ToString());
                   
//Release the waiting thread.
                   
Monitor.Pulse(m_smplQueue);
               
}
           
}
       
}
       
//Return the number of queue elements.
       
public int GetQueueCount()
       
{
           
return m_smplQueue.Count;
       
}

static void Main(string[] args)
       
{
           
//Create the MonitorSample object.
           
MonitorSample test = new MonitorSample();
           
//Create the first thread.
           
Thread tFirst = new Thread(new
ThreadStart(test.FirstThread));
           
//Create the second thread.
           
Thread tSecond = new Thread(new
ThreadStart(test.SecondThread));
           
//Start threads.
           
tFirst.Start();
           
tSecond.Start();
           
//wait to the end of the two threads
           
tFirst.Join();
           
tSecond.Join();
           
//Print the number of queue elements.
           
Console.WriteLine("Queue Count = " +
test.GetQueueCount().ToString());
       
}
    }
}