CountdownEvent CountdownEvent CountdownEvent CountdownEvent Class

定義

代表當計數到達零時收到訊號的同步處理原始物件。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
繼承
CountdownEventCountdownEventCountdownEventCountdownEvent
屬性
實作

範例

下列範例示範如何使用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

建構函式

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

使用指定的計數,初始化 CountdownEvent 類別的新執行個體。Initializes a new instance of CountdownEvent class with the specified count.

屬性

CurrentCount CurrentCount CurrentCount CurrentCount

取得設定事件時需要的剩餘訊號次數。Gets the number of remaining signals required to set the event.

InitialCount InitialCount InitialCount InitialCount

取得設定事件一開始時所需要的訊號次數。Gets the numbers of signals initially required to set the event.

IsSet IsSet IsSet IsSet

指出 CountdownEvent 物件的目前計數是否已達到零。Indicates whether the CountdownEvent object's current count has reached zero.

WaitHandle WaitHandle WaitHandle WaitHandle

取得用來等候事件獲得設定的 WaitHandleGets a WaitHandle that is used to wait for the event to be set.

方法

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

CountdownEvent 目前的計數遞增一。Increments the CountdownEvent's current count by one.

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

CountdownEvent 目前的計數遞增所指定的值。Increments the CountdownEvent's current count by a specified value.

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

釋放 CountdownEvent 類別目前的執行個體所使用的全部資源。Releases all resources used by the current instance of the CountdownEvent class.

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

釋放 CountdownEvent 所使用的 Unmanaged 資源,並選擇性釋放 Managed 資源。Releases the unmanaged resources used by the CountdownEvent, and optionally releases the managed resources.

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

判斷指定的物件是否等於目前的物件。Determines whether the specified object is equal to the current object.

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

做為預設雜湊函式。Serves as the default hash function.

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

取得目前執行個體的 TypeGets the Type of the current instance.

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

建立目前 Object 的淺層複本 (Shallow Copy)。Creates a shallow copy of the current Object.

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

CurrentCount 重設為 InitialCount 的值。Resets the CurrentCount to the value of InitialCount.

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

InitialCount 屬性重設為指定的值。Resets the InitialCount property to a specified value.

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

CountdownEvent 註冊訊號,並遞減 CurrentCount 的值。Registers a signal with the CountdownEvent, decrementing the value of CurrentCount.

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

CountdownEvent 註冊多個訊號,並將 CurrentCount 的值遞減指定的數量。Registers multiple signals with the CountdownEvent, decrementing the value of CurrentCount by the specified amount.

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

傳回代表目前物件的字串。Returns a string that represents the current object.

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

嘗試將 CurrentCount 遞增一。Attempts to increment CurrentCount by one.

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

嘗試以指定的值遞增 CurrentCountAttempts to increment CurrentCount by a specified value.

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

封鎖目前的執行緒,直到設定了 CountdownEvent 為止。Blocks the current thread until the CountdownEvent is set.

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

封鎖目前的執行緒,直到設定了 CountdownEvent 為止,同時觀察 CancellationTokenBlocks the current thread until the CountdownEvent is set, while observing a CancellationToken.

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

封鎖目前的執行緒,直到設定了 CountdownEvent 為止 (使用 32 位元帶正負號的整數以測量逾時)。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)

封鎖目前的執行緒,直到設定了 CountdownEvent 為止 (使用 32 位元帶正負號的整數以測量逾時),同時觀察 CancellationTokenBlocks 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)

封鎖目前的執行緒,直到設定了 CountdownEvent 為止 (使用 TimeSpan 以測量逾時)。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)

封鎖目前的執行緒,直到設定了 CountdownEvent 為止 (使用 TimeSpan 以測量逾時),同時觀察 CancellationTokenBlocks the current thread until the CountdownEvent is set, using a TimeSpan to measure the timeout, while observing a CancellationToken.

適用於

執行緒安全性

所有 public 和 protected 成員CountdownEvent是安全執行緒,而且用於同時從多個執行緒,但不包括Dispose(),它必須時,才會使用上的所有其他作業CountdownEvent已完成,和Reset(),它應該只用於當沒有其他執行緒同時存取事件。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.

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