WaitHandle 类
封装等待对共享资源的独占访问的操作系统特定的对象。
**命名空间:**System.Threading
**程序集:**mscorlib（在 mscorlib.dll 中）
语法
声明
<ComVisibleAttribute(True)> _
Public MustInherit Class WaitHandle
Inherits MarshalByRefObject
Implements IDisposable
用法
Dim instance As WaitHandle
[ComVisibleAttribute(true)]
public abstract class WaitHandle : MarshalByRefObject, IDisposable
[ComVisibleAttribute(true)]
public ref class WaitHandle abstract : public MarshalByRefObject, IDisposable
/** @attribute ComVisibleAttribute(true) */
public abstract class WaitHandle extends MarshalByRefObject implements IDisposable
ComVisibleAttribute(true)
public abstract class WaitHandle extends MarshalByRefObject implements IDisposable
备注
此类通常用作同步对象的基类。从 WaitHandle 派生的类定义一个信号传输机制以指示获取或释放对共享资源的独占访问，但使用继承的 WaitHandle 方法在等待访问共享资源时阻止。
使用此类的静态方法阻塞一个线程，直到一个或多个同步对象接收到信号。
示例
下面的代码示例演示当主线程使用 WaitHandle 类的静态 M:System.Threading.WaitHandle.WaitAny(System.Threading.WaitHandle[]) 和 WaitAll 方法等待任务完成时，两个线程可以如何完成后台任务。
Imports System
Imports System.Threading
NotInheritable Public Class App
' Define an array with two AutoResetEvent WaitHandles.
Private Shared waitHandles() As WaitHandle = _
{New AutoResetEvent(False), New AutoResetEvent(False)}
' Define a random number generator for testing.
Private Shared r As New Random()
<MTAThreadAttribute> _
Public Shared Sub Main()
' Queue two tasks on two different threads;
' wait until all tasks are completed.
Dim dt As DateTime = DateTime.Now
Console.WriteLine("Main thread is waiting for BOTH tasks to complete.")
ThreadPool.QueueUserWorkItem(AddressOf DoTask, waitHandles(0))
ThreadPool.QueueUserWorkItem(AddressOf DoTask, waitHandles(1))
WaitHandle.WaitAll(waitHandles)
' The time shown below should match the longest task.
Console.WriteLine("Both tasks are completed (time waited={0})", _
(DateTime.Now - dt).TotalMilliseconds)
' Queue up two tasks on two different threads;
' wait until any tasks are completed.
dt = DateTime.Now
Console.WriteLine()
Console.WriteLine("The main thread is waiting for either task to complete.")
ThreadPool.QueueUserWorkItem(AddressOf DoTask, waitHandles(0))
ThreadPool.QueueUserWorkItem(AddressOf DoTask, waitHandles(1))
Dim index As Integer = WaitHandle.WaitAny(waitHandles)
' The time shown below should match the shortest task.
Console.WriteLine("Task {0} finished first (time waited={1}).", _
index + 1,(DateTime.Now - dt).TotalMilliseconds)
End Sub 'Main
Shared Sub DoTask(ByVal state As [Object])
Dim are As AutoResetEvent = CType(state, AutoResetEvent)
Dim time As Integer = 1000 * r.Next(2, 10)
Console.WriteLine("Performing a task for {0} milliseconds.", time)
Thread.Sleep(time)
are.Set()
End Sub 'DoTask
End Class 'App
' This code produces output similar to the following:
'
' Main thread is waiting for BOTH tasks to complete.
' Performing a task for 7000 milliseconds.
' Performing a task for 4000 milliseconds.
' Both tasks are completed (time waited=7064.8052)
'
' The main thread is waiting for either task to complete.
' Performing a task for 2000 milliseconds.
' Performing a task for 2000 milliseconds.
' Task 1 finished first (time waited=2000.6528).
using System;
using System.Threading;
public sealed class App
{
// Define an array with two AutoResetEvent WaitHandles.
static WaitHandle[] waitHandles = new WaitHandle[]
{
new AutoResetEvent(false),
new AutoResetEvent(false)
};
// Define a random number generator for testing.
static Random r = new Random();
static void Main()
{
// Queue up two tasks on two different threads;
// wait until all tasks are completed.
DateTime dt = DateTime.Now;
Console.WriteLine("Main thread is waiting for BOTH tasks to complete.");
ThreadPool.QueueUserWorkItem(new WaitCallback(DoTask), waitHandles[0]);
ThreadPool.QueueUserWorkItem(new WaitCallback(DoTask), waitHandles[1]);
WaitHandle.WaitAll(waitHandles);
// The time shown below should match the longest task.
Console.WriteLine("Both tasks are completed (time waited={0})",
(DateTime.Now - dt).TotalMilliseconds);
// Queue up two tasks on two different threads;
// wait until any tasks are completed.
dt = DateTime.Now;
Console.WriteLine();
Console.WriteLine("The main thread is waiting for either task to complete.");
ThreadPool.QueueUserWorkItem(new WaitCallback(DoTask), waitHandles[0]);
ThreadPool.QueueUserWorkItem(new WaitCallback(DoTask), waitHandles[1]);
int index = WaitHandle.WaitAny(waitHandles);
// The time shown below should match the shortest task.
Console.WriteLine("Task {0} finished first (time waited={1}).",
index + 1, (DateTime.Now - dt).TotalMilliseconds);
}
static void DoTask(Object state)
{
AutoResetEvent are = (AutoResetEvent) state;
int time = 1000 * r.Next(2, 10);
Console.WriteLine("Performing a task for {0} milliseconds.", time);
Thread.Sleep(time);
are.Set();
}
}
// This code produces output similar to the following:
//
// Main thread is waiting for BOTH tasks to complete.
// Performing a task for 7000 milliseconds.
// Performing a task for 4000 milliseconds.
// Both tasks are completed (time waited=7064.8052)
//
// The main thread is waiting for either task to complete.
// Performing a task for 2000 milliseconds.
// Performing a task for 2000 milliseconds.
// Task 1 finished first (time waited=2000.6528).
using namespace System;
using namespace System::Threading;
public ref class WaitHandleExample
{
// Define a random number generator for testing.
private:
static Random^ random = gcnew Random();
public:
static void DoTask(Object^ state)
{
AutoResetEvent^ autoReset = (AutoResetEvent^) state;
int time = 1000 * random->Next(2, 10);
Console::WriteLine("Performing a task for {0} milliseconds.", time);
Thread::Sleep(time);
autoReset->Set();
}
};
int main()
{
// Define an array with two AutoResetEvent WaitHandles.
array<WaitHandle^>^ handles = gcnew array<WaitHandle^> {
gcnew AutoResetEvent(false), gcnew AutoResetEvent(false)};
// Queue up two tasks on two different threads;
// wait until all tasks are completed.
DateTime timeInstance = DateTime::Now;
Console::WriteLine("Main thread is waiting for BOTH tasks to " +
"complete.");
ThreadPool::QueueUserWorkItem(
gcnew WaitCallback(WaitHandleExample::DoTask), handles[0]);
ThreadPool::QueueUserWorkItem(
gcnew WaitCallback(WaitHandleExample::DoTask), handles[1]);
WaitHandle::WaitAll(handles);
// The time shown below should match the longest task.
Console::WriteLine("Both tasks are completed (time waited={0})",
(DateTime::Now - timeInstance).TotalMilliseconds);
// Queue up two tasks on two different threads;
// wait until any tasks are completed.
timeInstance = DateTime::Now;
Console::WriteLine();
Console::WriteLine("The main thread is waiting for either task to " +
"complete.");
ThreadPool::QueueUserWorkItem(
gcnew WaitCallback(WaitHandleExample::DoTask), handles[0]);
ThreadPool::QueueUserWorkItem(
gcnew WaitCallback(WaitHandleExample::DoTask), handles[1]);
int index = WaitHandle::WaitAny(handles);
// The time shown below should match the shortest task.
Console::WriteLine("Task {0} finished first (time waited={1}).",
index + 1, (DateTime::Now - timeInstance).TotalMilliseconds);
}
// This code produces the following sample output.
//
// Main thread is waiting for BOTH tasks to complete.
// Performing a task for 7000 milliseconds.
// Performing a task for 4000 milliseconds.
// Both tasks are completed (time waited=7064.8052)
// The main thread is waiting for either task to complete.
// Performing a task for 2000 milliseconds.
// Performing a task for 2000 milliseconds.
// Task 1 finished first (time waited=2000.6528).
继承层次结构
System.Object
System.MarshalByRefObject
System.Threading.WaitHandle
System.Threading.EventWaitHandle
System.Threading.Mutex
System.Threading.Semaphore
线程安全
此类型是线程安全的。
平台
Windows 98、Windows 2000 SP4、Windows CE、Windows Millennium Edition、Windows Mobile for Pocket PC、Windows Mobile for Smartphone、Windows Server 2003、Windows XP Media Center Edition、Windows XP Professional x64 Edition、Windows XP SP2、Windows XP Starter Edition
.NET Framework 并不是对每个平台的所有版本都提供支持。有关受支持版本的列表，请参见系统要求。
版本信息
.NET Framework
受以下版本支持：2.0、1.1、1.0
.NET Compact Framework
受以下版本支持：2.0、1.0
请参见
参考
WaitHandle 成员
System.Threading 命名空间