CountdownEvent CountdownEvent CountdownEvent CountdownEvent Class

Definição

Representa um primitivo de sincronização que é sinalizado quando sua contagem atinge zero.Represents a synchronization primitive that is signaled when its count reaches zero.

public ref class CountdownEvent : IDisposable
[System.Runtime.InteropServices.ComVisible(false)]
public class CountdownEvent : IDisposable
type CountdownEvent = class
    interface IDisposable
Public Class CountdownEvent
Implements IDisposable
Herança
CountdownEventCountdownEventCountdownEventCountdownEvent
Atributos
Implementações

Exemplos

O exemplo a seguir mostra como usar um CountdownEvent:The following example shows how to use a CountdownEvent:

using System;
using System.Collections.Concurrent;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

class Example
{
    static async Task Main()
    {
        // Initialize a queue and a CountdownEvent
        ConcurrentQueue<int> queue = new ConcurrentQueue<int>(Enumerable.Range(0, 10000));
        CountdownEvent cde = new CountdownEvent(10000); // initial count = 10000

        // This is the logic for all queue consumers
        Action consumer = () =>
        {
            int local;
            // decrement CDE count once for each element consumed from queue
            while (queue.TryDequeue(out local)) cde.Signal();
        };

        // Now empty the queue with a couple of asynchronous tasks
        Task t1 = Task.Factory.StartNew(consumer);
        Task t2 = Task.Factory.StartNew(consumer);

        // And wait for queue to empty by waiting on cde
        cde.Wait(); // will return when cde count reaches 0

        Console.WriteLine("Done emptying queue.  InitialCount={0}, CurrentCount={1}, IsSet={2}",
            cde.InitialCount, cde.CurrentCount, cde.IsSet);

        // Proper form is to wait for the tasks to complete, even if you that their work
        // is done already.
        await Task.WhenAll(t1, t2);

        // Resetting will cause the CountdownEvent to un-set, and resets InitialCount/CurrentCount
        // to the specified value
        cde.Reset(10);

        // AddCount will affect the CurrentCount, but not the InitialCount
        cde.AddCount(2);

        Console.WriteLine("After Reset(10), AddCount(2): InitialCount={0}, CurrentCount={1}, IsSet={2}",
            cde.InitialCount, cde.CurrentCount, cde.IsSet);

        // Now try waiting with cancellation
        CancellationTokenSource cts = new CancellationTokenSource();
        cts.Cancel(); // cancels the CancellationTokenSource
        try
        {
            cde.Wait(cts.Token);
        }
        catch (OperationCanceledException)
        {
            Console.WriteLine("cde.Wait(preCanceledToken) threw OCE, as expected");
        }
        finally
        {
           cts.Dispose();
        }
        // It's good to release a CountdownEvent when you're done with it.
        cde.Dispose();
    }
}
// The example displays the following output:
//    Done emptying queue.  InitialCount=10000, CurrentCount=0, IsSet=True
//    After Reset(10), AddCount(2): InitialCount=10, CurrentCount=12, IsSet=False
//    cde.Wait(preCanceledToken) threw OCE, as expected
Imports System.Collections.Concurrent
Imports System.Linq
Imports System.Threading
Imports System.Threading.Tasks

Module Example
    Sub Main()
        ' Initialize a queue and a CountdownEvent
        Dim queue As New ConcurrentQueue(Of Integer)(Enumerable.Range(0, 10000))
        Dim cde As New CountdownEvent(10000)
        ' initial count = 10000
        ' This is the logic for all queue consumers
        Dim consumer As Action =
            Sub()
                Dim local As Integer
                ' decrement CDE count once for each element consumed from queue
                While queue.TryDequeue(local)
                    cde.Signal()
                End While
            End Sub

        ' Now empty the queue with a couple of asynchronous tasks
        Dim t1 As Task = Task.Factory.StartNew(consumer)
        Dim t2 As Task = Task.Factory.StartNew(consumer)

        ' And wait for queue to empty by waiting on cde
        cde.Wait()
        ' will return when cde count reaches 0
        Console.WriteLine("Done emptying queue. InitialCount={0}, CurrentCount={1}, IsSet={2}", cde.InitialCount, cde.CurrentCount, cde.IsSet)

        ' Proper form is to wait for the tasks to complete, even if you know that their work
        ' is done already.
        Task.WaitAll(t1, t2)

        ' Resetting will cause the CountdownEvent to un-set, and resets InitialCount/CurrentCount
        ' to the specified value
        cde.Reset(10)

        ' AddCount will affect the CurrentCount, but not the InitialCount
        cde.AddCount(2)

        Console.WriteLine("After Reset(10), AddCount(2): InitialCount={0}, CurrentCount={1}, IsSet={2}", cde.InitialCount, cde.CurrentCount, cde.IsSet)

        ' Now try waiting with cancellation
        Dim cts As New CancellationTokenSource()
        cts.Cancel()
        ' cancels the CancellationTokenSource
        Try
            cde.Wait(cts.Token)
        Catch generatedExceptionName As OperationCanceledException
            Console.WriteLine("cde.Wait(preCanceledToken) threw OCE, as expected")
        Finally
           cts.Dispose()
        End Try

        ' It's good to release a CountdownEvent when you're done with it.
        cde.Dispose()
    End Sub
End Module
' The example displays the following output:
'    Done emptying queue.  InitialCount=10000, CurrentCount=0, IsSet=True
'    After Reset(10), AddCount(2): InitialCount=10, CurrentCount=12, IsSet=False
'    cde.Wait(preCanceledToken) threw OCE, as expected

Construtores

CountdownEvent(Int32) CountdownEvent(Int32) CountdownEvent(Int32) CountdownEvent(Int32)

Inicializa uma nova instância da classe CountdownEvent com a contagem especificada.Initializes a new instance of CountdownEvent class with the specified count.

Propriedades

CurrentCount CurrentCount CurrentCount CurrentCount

Obtém o número de sinais restantes necessárias para definir o evento.Gets the number of remaining signals required to set the event.

InitialCount InitialCount InitialCount InitialCount

Obtém os números de sinais inicialmente necessários para definir o evento.Gets the numbers of signals initially required to set the event.

IsSet IsSet IsSet IsSet

Indica se a contagem atual do objeto CountdownEvent chegou a zero.Indicates whether the CountdownEvent object's current count has reached zero.

WaitHandle WaitHandle WaitHandle WaitHandle

Obtém um WaitHandle que é usado para aguardar o evento a ser definido.Gets a WaitHandle that is used to wait for the event to be set.

Métodos

AddCount() AddCount() AddCount() AddCount()

Incrementa a contagem atual de CountdownEvent em um.Increments the CountdownEvent's current count by one.

AddCount(Int32) AddCount(Int32) AddCount(Int32) AddCount(Int32)

Incrementa a contagem atual de CountdownEvent em um valor especificado.Increments the CountdownEvent's current count by a specified value.

Dispose() Dispose() Dispose() Dispose()

Libera todos os recursos usados pela instância atual da classe CountdownEvent.Releases all resources used by the current instance of the CountdownEvent class.

Dispose(Boolean) Dispose(Boolean) Dispose(Boolean) Dispose(Boolean)

Libera os recursos não gerenciados usados pelo CountdownEvent e opcionalmente libera os recursos gerenciados.Releases the unmanaged resources used by the CountdownEvent, and optionally releases the managed resources.

Equals(Object) Equals(Object) Equals(Object) Equals(Object)

Determina se o objeto especificado é igual ao objeto atual.Determines whether the specified object is equal to the current object.

(Inherited from Object)
GetHashCode() GetHashCode() GetHashCode() GetHashCode()

Serve como a função de hash padrão.Serves as the default hash function.

(Inherited from Object)
GetType() GetType() GetType() GetType()

Obtém o Type da instância atual.Gets the Type of the current instance.

(Inherited from Object)
MemberwiseClone() MemberwiseClone() MemberwiseClone() MemberwiseClone()

Cria uma cópia superficial do Object atual.Creates a shallow copy of the current Object.

(Inherited from Object)
Reset() Reset() Reset() Reset()

Redefine o CurrentCount para o valor de InitialCount.Resets the CurrentCount to the value of InitialCount.

Reset(Int32) Reset(Int32) Reset(Int32) Reset(Int32)

Redefine a propriedade InitialCount com um valor especificado.Resets the InitialCount property to a specified value.

Signal() Signal() Signal() Signal()

Registra um sinal com o CountdownEvent, diminuindo o valor de CurrentCount.Registers a signal with the CountdownEvent, decrementing the value of CurrentCount.

Signal(Int32) Signal(Int32) Signal(Int32) Signal(Int32)

Registra vários sinais com o CountdownEvent, diminuindo o valor de CurrentCount pelo valor especificado.Registers multiple signals with the CountdownEvent, decrementing the value of CurrentCount by the specified amount.

ToString() ToString() ToString() ToString()

Retorna uma cadeia de caracteres que representa o objeto atual.Returns a string that represents the current object.

(Inherited from Object)
TryAddCount() TryAddCount() TryAddCount() TryAddCount()

Tenta incrementar CurrentCount por um.Attempts to increment CurrentCount by one.

TryAddCount(Int32) TryAddCount(Int32) TryAddCount(Int32) TryAddCount(Int32)

Tenta incrementar CurrentCount em um valor especificado.Attempts to increment CurrentCount by a specified value.

Wait() Wait() Wait() Wait()

Bloqueia o thread atual até que o CountdownEvent seja definido.Blocks the current thread until the CountdownEvent is set.

Wait(CancellationToken) Wait(CancellationToken) Wait(CancellationToken) Wait(CancellationToken)

Bloqueia o thread atual até que o CountdownEvent seja definido, enquanto observa um CancellationToken.Blocks the current thread until the CountdownEvent is set, while observing a CancellationToken.

Wait(Int32) Wait(Int32) Wait(Int32) Wait(Int32)

Bloqueia o thread atual até que o CountdownEvent seja definido, usando um inteiro com sinal de 32 bits para medir o tempo limite.Blocks the current thread until the CountdownEvent is set, using a 32-bit signed integer to measure the timeout.

Wait(Int32, CancellationToken) Wait(Int32, CancellationToken) Wait(Int32, CancellationToken) Wait(Int32, CancellationToken)

Bloqueia o thread atual até que o CountdownEvent seja definido, usando um inteiro com sinal de 32 bits para medir o tempo limite, enquanto observa um CancellationToken.Blocks the current thread until the CountdownEvent is set, using a 32-bit signed integer to measure the timeout, while observing a CancellationToken.

Wait(TimeSpan) Wait(TimeSpan) Wait(TimeSpan) Wait(TimeSpan)

Bloqueia o thread atual até que o CountdownEvent seja definido, usando um TimeSpan para medir o tempo limite.Blocks the current thread until the CountdownEvent is set, using a TimeSpan to measure the timeout.

Wait(TimeSpan, CancellationToken) Wait(TimeSpan, CancellationToken) Wait(TimeSpan, CancellationToken) Wait(TimeSpan, CancellationToken)

Bloqueia o thread atual até que o CountdownEvent seja definido, usando um TimeSpan para medir o tempo limite, enquanto observa um CancellationToken.Blocks the current thread until the CountdownEvent is set, using a TimeSpan to measure the timeout, while observing a CancellationToken.

Aplica-se a

Acesso thread-safe

Todos os membros públicos e protegidos da CountdownEvent são thread-safe e podem ser usados simultaneamente de vários threads, com exceção de Dispose(), que deve ser usado somente quando todas as outras operações no CountdownEvent tiver concluído e Reset(), que só deve ser usado quando nenhum outro thread está acessando o evento.All public and protected members of CountdownEvent are thread-safe and may be used concurrently from multiple threads, with the exception of Dispose(), which must only be used when all other operations on the CountdownEvent have completed, and Reset(), which should only be used when no other threads are accessing the event.

Veja também