EventWaitHandle 类

定义

命名空间:

System.Threading

程序集:

System.Threading.dll

Source:

EventWaitHandle.cs

表示一个线程同步事件。

public ref class EventWaitHandle : System::Threading::WaitHandle

public class EventWaitHandle : System.Threading.WaitHandle

type EventWaitHandle = class
    inherit WaitHandle

Public Class EventWaitHandle
Inherits WaitHandle

继承

Object

MarshalByRefObject

WaitHandle

EventWaitHandle

派生

System.Threading.AutoResetEvent

System.Threading.ManualResetEvent

示例

下面的代码示例使用 SignalAndWait(WaitHandle, WaitHandle) 方法重载允许main线程向阻塞的线程发出信号，然后等待线程完成任务。

该示例启动五个 EventWaitHandle 线程，并允许它们阻止使用 EventResetMode.AutoReset 标志创建的 ，然后在用户每次按 Enter 键时释放一个线程。 然后，该示例将另外五个 EventWaitHandle 线程排队，并使用使用 EventResetMode.ManualReset 标志创建的 释放它们。

using namespace System;
using namespace System::Threading;

public ref class Example
{
private:
   // The EventWaitHandle used to demonstrate the difference
   // between AutoReset and ManualReset synchronization events.
   //
   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.
   //
   static __int64 threadCount = 0;

   // An AutoReset event that allows the main thread to block
   // until an exiting thread has decremented the count.
   //
   static EventWaitHandle^ clearCount =
      gcnew EventWaitHandle( false,EventResetMode::AutoReset );

public:
   [MTAThread]
   static void main()
   {
      // Create an AutoReset EventWaitHandle.
      //
      ewh = gcnew 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 = gcnew Thread(
            gcnew 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( threadCount ) < 5 )
      {
         Thread::Sleep( 500 );
      }

      // Release one thread each time the user presses ENTER,
      // until all threads have been released.
      //
      while ( Interlocked::Read( threadCount ) > 0 )
      {
         Console::WriteLine( L"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 = gcnew EventWaitHandle( false,EventResetMode::ManualReset );
      
      // Create and start five more numbered threads.
      //
      for ( int i = 0; i <= 4; i++ )
      {
         Thread^ t = gcnew Thread(
            gcnew ParameterizedThreadStart( ThreadProc ) );
         t->Start( i );
      }
      
      // Wait until all the threads have started and blocked.
      //
      while ( Interlocked::Read( threadCount ) < 5 )
      {
         Thread::Sleep( 500 );
      }

      // Because the EventWaitHandle was created with
      // ManualReset mode, signaling it releases all the
      // waiting threads.
      //
      Console::WriteLine( L"Press ENTER to release the waiting threads." );
      Console::ReadLine();
      ewh->Set();

   }

   static void ThreadProc( Object^ data )
   {
      int index = static_cast<Int32>(data);

      Console::WriteLine( L"Thread {0} blocks.", data );
      // Increment the count of blocked threads.
      Interlocked::Increment( threadCount );
      
      // Wait on the EventWaitHandle.
      ewh->WaitOne();

      Console::WriteLine( L"Thread {0} exits.", data );
      // Decrement the count of blocked threads.
      Interlocked::Decrement( threadCount );
      
      // After signaling ewh, the main thread blocks on
      // clearCount until the signaled thread has
      // decremented the count. Signal it now.
      //
      clearCount->Set();
   }
};

using System;
using System.Threading;

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();
    }

    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();
    }
}

Imports System.Threading

Public Class Example

    ' The EventWaitHandle used to demonstrate the difference
    ' between AutoReset and ManualReset synchronization events.
    '
    Private Shared ewh As EventWaitHandle

    ' 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 Shared threadCount As Long = 0

    ' An AutoReset event that allows the main thread to block
    ' until an exiting thread has decremented the count.
    '
    Private Shared clearCount As New EventWaitHandle(False, _
        EventResetMode.AutoReset)

    <MTAThread> _
    Public Shared Sub 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 i As Integer = 0 To 4
            Dim t As New Thread(AddressOf ThreadProc)
            t.Start(i)
        Next 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(threadCount) < 5
            Thread.Sleep(500)
        End While

        ' Release one thread each time the user presses ENTER,
        ' until all threads have been released.
        '
        While Interlocked.Read(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)
        End While
        Console.WriteLine()

        ' Create a ManualReset EventWaitHandle.
        '
        ewh = New EventWaitHandle(False, EventResetMode.ManualReset)

        ' Create and start five more numbered threads.
        '
        For i As Integer = 0 To 4
            Dim t As New Thread(AddressOf ThreadProc)
            t.Start(i)
        Next i

        ' Wait until all the threads have started and blocked.
        '
        While Interlocked.Read(threadCount) < 5
            Thread.Sleep(500)
        End While

        ' 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()
        
    End Sub

    Public Shared Sub ThreadProc(ByVal data As Object)
        Dim index As Integer = CInt(data)

        Console.WriteLine("Thread {0} blocks.", data)
        ' Increment the count of blocked threads.
        Interlocked.Increment(threadCount)

        ' Wait on the EventWaitHandle.
        ewh.WaitOne()

        Console.WriteLine("Thread {0} exits.", data)
        ' Decrement the count of blocked threads.
        Interlocked.Decrement(threadCount)

        ' After signaling ewh, the main thread blocks on
        ' clearCount until the signaled thread has 
        ' decremented the count. Signal it now.
        '
        clearCount.Set()
    End Sub
End Class

注解

类 EventWaitHandle 允许线程通过信号相互通信。 通常， 上的一个或多个线程阻塞， EventWaitHandle 直到未阻止的线程调用 Set 方法，释放一个或多个被阻止的线程。 线程可以通过在 Visual Basic) WaitHandle.SignalAndWait 方法中调用 static (Shared 来发出信号EventWaitHandle，然后阻止该线程。

注意

类 EventWaitHandle 提供对命名系统同步事件的访问权限。

已发出信号的 EventWaitHandle 的行为取决于其重置模式。 EventWaitHandle在释放单个等待线程后，使用 EventResetMode.AutoReset 标志创建的 在发出信号后自动重置。 在 Reset 方法获得调用前，一直向使用 EventResetMode.ManualReset 标志创建的 EventWaitHandle 发出信号。

自动重置事件提供对资源的独占访问权限。 如果向自动重置事件发出信号时没有线程正在等待，此信号会一直发出到有线程尝试在等待句柄上等待。 此时，事件会释放相应线程并立即重置自身，同时阻止后续线程。

手动重置事件类似于门。 如果未发出事件信号，等待它的线程将阻塞。 发出事件信号时，将释放所有等待的线程，并且事件保持信号 (也就是说，在调用其 Reset 方法之前，后续等待不会阻止) 。 当一个线程必须在其他线程继续之前完成某个活动时，手动重置事件非常有用。

EventWaitHandle对象可与 Visual Basic) 和 WaitHandle.WaitAny 方法中的 (WaitHandle.WaitAll 一起使用static。Shared

有关详细信息，请参阅同步基元概述一文的线程交互或信号部分。

注意

默认情况下，命名事件不限于创建它的用户。 其他用户可能能够打开和使用事件，包括通过不当设置或重置事件来干扰事件。 若要限制对特定用户的访问，可以使用构造函数重载 或 EventWaitHandleAcl ，并在创建命名事件时传入 EventWaitHandleSecurity 。 避免在可能有不受信任的用户运行代码的系统上使用没有访问限制的命名事件。

构造函数

EventWaitHandle(Boolean, EventResetMode)	初始化 EventWaitHandle 类的新实例，并指定等待句柄最初是否处于终止状态，以及它是自动重置还是手动重置。
EventWaitHandle(Boolean, EventResetMode, String)	初始化 EventWaitHandle 类的新实例，并指定在此调用后创建的等待句柄最初是否处于终止状态，它是自动重置还是手动重置，以及系统同步事件的名称。
EventWaitHandle(Boolean, EventResetMode, String, Boolean)	初始化 EventWaitHandle 类的新实例，指定如果将等待句柄作为此调用的结果而创建，最初是否通过信号通知此句柄；指定是否自动或手动重置系统同步事件的名称，以及一个布尔变量，在调用后其值指示是否创建了命名的系统事件。

字段

WaitTimeout

指示在任何等待句柄终止之前 WaitAny(WaitHandle[], Int32, Boolean) 操作已超时。 此字段为常数。 (继承自 WaitHandle)

属性

Handle	已过时. 获取或设置本机操作系统句柄。 (继承自 WaitHandle)
SafeWaitHandle	获取或设置本机操作系统句柄。 (继承自 WaitHandle)

方法

Close()	释放由当前 WaitHandle 占用的所有资源。 (继承自 WaitHandle)
CreateObjRef(Type)	创建一个对象，该对象包含生成用于与远程对象进行通信的代理所需的全部相关信息。 (继承自 MarshalByRefObject)
Dispose()	释放 WaitHandle 类的当前实例所使用的所有资源。 (继承自 WaitHandle)
Dispose(Boolean)	当在派生类中重写时，释放 WaitHandle 使用的非托管资源，并且可选择释放托管资源。 (继承自 WaitHandle)
Equals(Object)	确定指定对象是否等于当前对象。 (继承自 Object)
GetHashCode()	作为默认哈希函数。 (继承自 Object)
GetLifetimeService()	已过时. 检索控制此实例的生存期策略的当前生存期服务对象。 (继承自 MarshalByRefObject)
GetType()	获取当前实例的 Type。 (继承自 Object)
InitializeLifetimeService()	已过时. 获取生存期服务对象来控制此实例的生存期策略。 (继承自 MarshalByRefObject)
MemberwiseClone()	创建当前 Object 的浅表副本。 (继承自 Object)
MemberwiseClone(Boolean)	创建当前 MarshalByRefObject 对象的浅表副本。 (继承自 MarshalByRefObject)
OpenExisting(String)	打开指定名称为同步事件（如果已经存在）。
Reset()	将事件状态设置为非终止状态，导致线程阻止。
Set()	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。
ToString()	返回表示当前对象的字符串。 (继承自 Object)
TryOpenExisting(String, EventWaitHandle)	打开指定的命名同步事件（如果已经存在），返回指示操作是否成功的值。
WaitOne()	阻止当前线程，直到当前 WaitHandle 收到信号。 (继承自 WaitHandle)
WaitOne(Int32)	阻止当前线程，直到当前 WaitHandle 收到信号，同时使用 32 位带符号整数指定时间间隔（以毫秒为单位）。 (继承自 WaitHandle)
WaitOne(Int32, Boolean)	阻止当前线程，直到当前的 WaitHandle 收到信号为止，同时使用 32 位带符号整数指定时间间隔，并指定是否在等待之前退出同步域。 (继承自 WaitHandle)
WaitOne(TimeSpan)	阻止当前线程，直到当前实例收到信号，同时使用 TimeSpan 指定时间间隔。 (继承自 WaitHandle)
WaitOne(TimeSpan, Boolean)	阻止当前线程，直到当前实例收到信号为止，同时使用 TimeSpan 指定时间间隔，并指定是否在等待之前退出同步域。 (继承自 WaitHandle)

扩展方法

GetAccessControl(EventWaitHandle)	返回指定的 handle 的安全描述符。
SetAccessControl(EventWaitHandle, EventWaitHandleSecurity)	设置指定事件等待句柄的安全描述符。
GetSafeWaitHandle(WaitHandle)	获取本机操作系统等待句柄的安全句柄。
SetSafeWaitHandle(WaitHandle, SafeWaitHandle)	设置本机操作系统等待句柄的安全句柄。

线程安全性

此类型是线程安全的。

另请参阅

• WaitHandle
• AutoResetEvent
• ManualResetEvent
• 托管线程
• 同步基元概述