在C#多线程编程中，这两个类几乎是不可或缺的,他们的用法/声明都很类似，那么区别在哪里了?
Set方法将信号置为发送状态 Reset方法将信号置为不发送状态 WaitOne等待信号的发送
其实,从名字就可以看出一点端倪 ,一个手动,一个自动，这个手动和自动实际指的是在Reset方法的处理上,如下面例子
public AutoResetEvent autoevent=new AutoResetEvent(true);
public ManualResetEvent manualevent=new ManualResetEvent(true);
默认信号都处于发送状态,
autoevent.WaitOne();
manualevent.WaitOne();
如果 某个线程调用上面该方法,则当信号处于发送状态时,该线程会得到信号,得以继续执行
差别就在调用后,autoevent.WaitOne()每次只允许一个线程进入,当某个线程得到信号(也就是有其他线程调用
了autoevent.Set()方法后)后,autoevent会自动又将信号置为不发送状态,则其他调用WaitOne的线程只有继续等待.也就是说,autoevent一次只唤醒一个线程
而manualevent则可以唤醒多个线程,因为当某个线程调用了set方法后,其他调用waitone的线程获得信号得以继续执行,而manualevent不会自动将信号置为不发送.也就是说,除非手工调用了manualevent.Reset().方法,则
manualevent将一直保持有信号状态,manualevent也就可以同时唤醒多个线程继续执行
1. Set() 方法 将事件状态设置为终止状态，允许一个或多个等待线程继续。
对于Auto信号 Set 方法释放单个线程。如果没有等待线程，等待句柄将一直保持终止状态，直到某个线程尝试等待它，或者直到它Reset() 方法被调用。
对于Manual信号 调用 Set 方法将使等待句柄一直保持终止状态，直到它的 Reset 方法被调用。(也就是说等待这个信号的一个或多个 线路能继续运行，如果不调用Reset()就不终止）
2. Reset()方法 将事件状态设置为非终止状态，导致线程阻止。
关于ManualRestEvents 与AutoResetEvents 中代码，描述ManualResetEvents一次能换醒多个线程，而AutoResetEvents只能一次换醒一个，一个一个换醒,(一个运行后，AutoResetEvents会自己设置为不发送或都叫非终止状态
public class Example { // The EventWaitHandle used to demonstrate the difference // between AutoReset and ManualReset synchronization events. // private static EventWaitHandle ewh;
// A counter to make sure all threads are started and // blocked before any are released. A Long is used to show // the use of the 64-bit Interlocked methods. // private static long threadCount = 0;
// An AutoReset event that allows the main thread to block // until an exiting thread has decremented the count. // private static EventWaitHandle clearCount = new EventWaitHandle(false, EventResetMode.AutoReset);
[MTAThread] public static void Main() { // Create an AutoReset EventWaitHandle. // ewh = new EventWaitHandle(false, EventResetMode.AutoReset);
// Create and start five numbered threads. Use the // ParameterizedThreadStart delegate, so the thread // number can be passed as an argument to the Start // method. for (int i = 0; i <= 4; i++) { Thread t = new Thread( new ParameterizedThreadStart(ThreadProc) ); t.Start(i); }
// Wait until all the threads have started and blocked. // When multiple threads use a 64-bit value on a 32-bit // system, you must access the value through the // Interlocked class to guarantee thread safety. // while (Interlocked.Read(ref threadCount) < 5) { Thread.Sleep(500); }
// Release one thread each time the user presses ENTER, // until all threads have been released. // while (Interlocked.Read(ref threadCount) > 0) { Console.WriteLine("Press ENTER to release a waiting thread."); Console.ReadLine();
// SignalAndWait signals the EventWaitHandle, which // releases exactly one thread before resetting, // because it was created with AutoReset mode. // SignalAndWait then blocks on clearCount, to // allow the signaled thread to decrement the count // before looping again. // WaitHandle.SignalAndWait(ewh, clearCount); } Console.WriteLine();
// Create a ManualReset EventWaitHandle. // ewh = new EventWaitHandle(false, EventResetMode.ManualReset);
// Create and start five more numbered threads. // for(int i=0; i<=4; i++) { Thread t = new Thread( new ParameterizedThreadStart(ThreadProc) ); t.Start(i); }
// Wait until all the threads have started and blocked. // while (Interlocked.Read(ref threadCount) < 5) { Thread.Sleep(500); }
// Because the EventWaitHandle was created with // ManualReset mode, signaling it releases all the // waiting threads. // Console.WriteLine("Press ENTER to release the waiting threads."); Console.ReadLine(); ewh.Set();
Console.ReadLine(); }
public static void ThreadProc(object data) { int index = (int) data;
Console.WriteLine("Thread {0} blocks.", data); // Increment the count of blocked threads. Interlocked.Increment(ref threadCount);
// Wait on the EventWaitHandle. ewh.WaitOne();
Console.WriteLine("Thread {0} exits.", data); // Decrement the count of blocked threads. Interlocked.Decrement(ref threadCount);
// After signaling ewh, the main thread blocks on // clearCount until the signaled thread has // decremented the count. Signal it now. // clearCount.Set(); } }
结果图:
转载：http://http://blog.csdn.net/tijichen/archive/2005/03/02/307531.aspx
