EventWaitHandle.Set Método
Definición
Importante
Parte de la información hace referencia a la versión preliminar del producto, que puede haberse modificado sustancialmente antes de lanzar la versión definitiva. Microsoft no otorga ninguna garantía, explícita o implícita, con respecto a la información proporcionada aquí.
Establece el estado del evento en señalado, permitiendo que uno o varios subprocesos en espera continúen.
public:
bool Set();public bool Set ();member this.Set : unit -> boolPublic Function Set () As BooleanDevoluciones
true si la operación se realiza correctamente; en caso contrario, false.
Excepciones
El método Close() se llamó previamente en este EventWaitHandle.
Ejemplos
En el ejemplo de código siguiente se usa la sobrecarga del SignalAndWait(WaitHandle, WaitHandle) método para permitir que el subproceso principal indique un subproceso bloqueado y espere a que el subproceso finalice una tarea.
El ejemplo inicia cinco subprocesos y les permite bloquear en un EventWaitHandle creado con la EventResetMode.AutoReset marca y, a continuación, libera un subproceso cada vez que el usuario presiona la tecla Entrar . A continuación, en el ejemplo se ponen en cola otros cinco subprocesos y se liberan todos con un EventWaitHandle creado con la EventResetMode.ManualReset marca .
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
Comentarios
Para un EventWaitHandle con EventResetMode.AutoReset (incluido AutoResetEvent), el Set método libera un único subproceso. Si no hay subprocesos en espera, el identificador de espera permanece señalado hasta que un subproceso intenta esperar en él o hasta que se llama a su Reset método.
Importante
No hay ninguna garantía de que cada llamada al Set método libere un subproceso de un EventWaitHandle cuyo modo de restablecimiento sea EventResetMode.AutoReset. Si dos llamadas están demasiado cerca, de modo que la segunda llamada se produzca antes de que se libere un subproceso, solo se libera un subproceso. Es como si no se hubiera producido la segunda llamada. Además, si Set se llama cuando no hay ningún subproceso en espera y ya EventWaitHandle está señalado, la llamada no tiene ningún efecto.
Para un EventWaitHandle con EventResetMode.ManualReset (incluido ManualResetEvent), al llamar al método deja el Set identificador de espera en un estado señalado hasta que se llama a su Reset método.