using System; using System.Collections; using System.Threading;namespace MonitorCS2 { /// <summary> /// Summary description for Class1. /// </summary> class MonitorSample { //Define the queue to safe thread access. private Queue m_inputQueue; public MonitorSample() { m_inputQueue = new Queue(); } //Add an element to the queue and obtain the monitor lock for the queue object. public void AddElement(object qValue) { //Lock the queue. Monitor.Enter(m_inputQueue); //Add element m_inputQueue.Enqueue(qValue); //Unlock the queue. Monitor.Exit(m_inputQueue); } //Try to add an element to the queue. //Add the element to the queue only if the queue object is unlocked. public bool AddElementWithoutWait(object qValue) { //Determine whether the queue is locked if(!Monitor.TryEnter(m_inputQueue)) return false; m_inputQueue.Enqueue(qValue); Monitor.Exit(m_inputQueue); return true; } //Try to add an element to the queue. //Add the element to the queue only if during the specified time the queue object will be unlocked. public bool WaitToAddElement(object qValue, int waitTime) { //Wait while the queue is locked. if(!Monitor.TryEnter(m_inputQueue,waitTime)) return false; m_inputQueue.Enqueue(qValue); Monitor.Exit(m_inputQueue); return true; }
//Delete all elements that equal the given object and obtain the monitor lock for the queue object. public void DeleteElement(object qValue) { //Lock the queue. Monitor.Enter(m_inputQueue); int counter = m_inputQueue.Count; while(counter > 0) { //Check each element. object elm = m_inputQueue.Dequeue(); if(!elm.Equals(qValue)) { m_inputQueue.Enqueue(elm); } --counter; } //Unlock the queue. Monitor.Exit(m_inputQueue); }
//Print all queue elements. public void PrintAllElements() { //Lock the queue. Monitor.Enter(m_inputQueue); IEnumerator elmEnum = m_inputQueue.GetEnumerator(); while(elmEnum.MoveNext()) { //Print the next element. Console.WriteLine(elmEnum.Current.ToString()); } //Unlock the queue. Monitor.Exit(m_inputQueue); } static void Main(string[] args) { MonitorSample sample = new MonitorSample();
for(int i = 0; i < 30; i++) sample.AddElement(i); sample.PrintAllElements(); sample.DeleteElement(0); sample.DeleteElement(10); sample.DeleteElement(20); sample.PrintAllElements(); } } }
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官方文档说的很清楚...不能保证任何实例成员是线程安全的...解决方法说的也很清楚...在整个枚举过程中锁定集合,或者捕捉由于其他线程进行的更改而引发的异常...
即使一个集合已进行同步,其他线程仍可以修改该集合,这将导致枚举数引发异常
.net采用的同步方法是,如果别的线程修改了,foreach将会导致异常
using System.Collections;
using System.Threading;namespace MonitorCS2
{
/// <summary>
/// Summary description for Class1.
/// </summary>
class MonitorSample
{
//Define the queue to safe thread access.
private Queue m_inputQueue; public MonitorSample()
{
m_inputQueue = new Queue();
} //Add an element to the queue and obtain the monitor lock for the queue object.
public void AddElement(object qValue)
{
//Lock the queue.
Monitor.Enter(m_inputQueue);
//Add element
m_inputQueue.Enqueue(qValue);
//Unlock the queue.
Monitor.Exit(m_inputQueue);
} //Try to add an element to the queue.
//Add the element to the queue only if the queue object is unlocked.
public bool AddElementWithoutWait(object qValue)
{
//Determine whether the queue is locked
if(!Monitor.TryEnter(m_inputQueue))
return false;
m_inputQueue.Enqueue(qValue); Monitor.Exit(m_inputQueue);
return true;
} //Try to add an element to the queue.
//Add the element to the queue only if during the specified time the queue object will be unlocked.
public bool WaitToAddElement(object qValue, int waitTime)
{
//Wait while the queue is locked.
if(!Monitor.TryEnter(m_inputQueue,waitTime))
return false;
m_inputQueue.Enqueue(qValue);
Monitor.Exit(m_inputQueue); return true;
}
//Delete all elements that equal the given object and obtain the monitor lock for the queue object.
public void DeleteElement(object qValue)
{
//Lock the queue.
Monitor.Enter(m_inputQueue);
int counter = m_inputQueue.Count;
while(counter > 0)
{
//Check each element.
object elm = m_inputQueue.Dequeue();
if(!elm.Equals(qValue))
{
m_inputQueue.Enqueue(elm);
}
--counter;
}
//Unlock the queue.
Monitor.Exit(m_inputQueue);
}
//Print all queue elements.
public void PrintAllElements()
{
//Lock the queue.
Monitor.Enter(m_inputQueue);
IEnumerator elmEnum = m_inputQueue.GetEnumerator();
while(elmEnum.MoveNext())
{
//Print the next element.
Console.WriteLine(elmEnum.Current.ToString());
}
//Unlock the queue.
Monitor.Exit(m_inputQueue);
} static void Main(string[] args)
{
MonitorSample sample = new MonitorSample();
for(int i = 0; i < 30; i++)
sample.AddElement(i);
sample.PrintAllElements();
sample.DeleteElement(0);
sample.DeleteElement(10);
sample.DeleteElement(20);
sample.PrintAllElements(); }
}
}