CountdownEvent CountdownEvent CountdownEvent CountdownEvent Class

Definizione

Rappresenta una primitiva di sincronizzazione segnalata quando il relativo conteggio raggiunge lo 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
Ereditarietà
CountdownEventCountdownEventCountdownEventCountdownEvent
Attributi
Implementazioni

Esempi

Nell'esempio seguente viene illustrato come utilizzare un CountdownEventoggetto: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

Costruttori

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

Inizializza una nuova istanza della classe CountdownEvent con il conteggio specificato.Initializes a new instance of CountdownEvent class with the specified count.

Proprietà

CurrentCount CurrentCount CurrentCount CurrentCount

Ottiene il numero di segnali restanti necessari per impostare l'evento.Gets the number of remaining signals required to set the event.

InitialCount InitialCount InitialCount InitialCount

Ottiene il numero di segnali necessari inizialmente per impostare l'evento.Gets the numbers of signals initially required to set the event.

IsSet IsSet IsSet IsSet

Indica se il conteggio corrente dell'oggetto CountdownEvent ha raggiunto lo zero.Indicates whether the CountdownEvent object's current count has reached zero.

WaitHandle WaitHandle WaitHandle WaitHandle

Ottiene un oggetto WaitHandle utilizzato per attendere l'impostazione dell'evento.Gets a WaitHandle that is used to wait for the event to be set.

Metodi

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

Incrementa di uno il conteggio corrente di CountdownEvent.Increments the CountdownEvent's current count by one.

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

Incrementa di un valore specificato il conteggio corrente di CountdownEvent.Increments the CountdownEvent's current count by a specified value.

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

Rilascia tutte le risorse usate dall'istanza corrente della classe CountdownEvent.Releases all resources used by the current instance of the CountdownEvent class.

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

Rilascia le risorse non gestite usate dall'oggetto CountdownEvent e, facoltativamente, le risorse gestite.Releases the unmanaged resources used by the CountdownEvent, and optionally releases the managed resources.

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

Determina se l'oggetto specificato è uguale all'oggetto corrente.Determines whether the specified object is equal to the current object.

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

Funge da funzione hash predefinita.Serves as the default hash function.

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

Ottiene l'oggetto Type dell'istanza corrente.Gets the Type of the current instance.

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

Crea una copia superficiale dell'oggetto Object corrente.Creates a shallow copy of the current Object.

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

Reimposta CurrentCount sul valore di InitialCount.Resets the CurrentCount to the value of InitialCount.

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

Reimposta la proprietà InitialCount al valore specificato.Resets the InitialCount property to a specified value.

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

Registra un segnale con l'oggetto CountdownEvent, decrementando il valore di CurrentCount.Registers a signal with the CountdownEvent, decrementing the value of CurrentCount.

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

Registra più segnali con l'oggetto CountdownEvent, decrementandone il valore di CurrentCount della quantità specificata.Registers multiple signals with the CountdownEvent, decrementing the value of CurrentCount by the specified amount.

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

Restituisce una stringa che rappresenta l'oggetto corrente.Returns a string that represents the current object.

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

Tenta di incrementare CurrentCount di uno.Attempts to increment CurrentCount by one.

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

Tenta di incrementare CurrentCount in base a un valore specificato.Attempts to increment CurrentCount by a specified value.

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

Blocca il thread corrente finché l'oggetto CountdownEvent non viene impostato.Blocks the current thread until the CountdownEvent is set.

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

Blocca il thread corrente finché l'oggetto CountdownEvent non viene impostato, al contempo osservando un oggetto CancellationToken.Blocks the current thread until the CountdownEvent is set, while observing a CancellationToken.

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

Blocca il thread corrente finché l'oggetto CountdownEvent non viene impostato, utilizzando un intero con segno a 32 bit per misurare il timeout.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)

Blocca il thread corrente finché l'oggetto CountdownEvent non viene impostato, utilizzando un intero con segno a 32 bit per misurare il timeout e al contempo osservando un oggetto 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)

Blocca il thread corrente finché l'oggetto CountdownEvent non viene impostato, utilizzando un oggetto TimeSpan per misurare il timeout.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)

Blocca il thread corrente finché l'oggetto CountdownEvent non viene impostato, utilizzando un oggetto TimeSpan per misurare il timeout e al contempo osservando un oggetto CancellationToken.Blocks the current thread until the CountdownEvent is set, using a TimeSpan to measure the timeout, while observing a CancellationToken.

Si applica a

Thread safety

Tutti i membri pubblici e protetti CountdownEvent di sono thread-safe e possono essere usati contemporaneamente da più thread, ad eccezione di Dispose(), che deve essere usato solo quando tutte le altre operazioni nell'oggetto CountdownEvent sono state completate e Reset(), che deve essere usato solo quando nessun altro thread accede all'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.

Vedi anche