CountdownEvent CountdownEvent CountdownEvent CountdownEvent Class

定义

表示在计数变为零时处于有信号状态的同步基元。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
继承
CountdownEventCountdownEventCountdownEventCountdownEvent
属性
实现

示例

下面的示例演示如何使用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

构造函数

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

使用指定计数初始化 CountdownEvent 类的新实例。Initializes a new instance of CountdownEvent class with the specified count.

属性

CurrentCount CurrentCount CurrentCount CurrentCount

获取设置事件时所必需的剩余信号数。Gets the number of remaining signals required to set the event.

InitialCount InitialCount InitialCount InitialCount

获取设置事件时最初必需的信号数。Gets the numbers of signals initially required to set the event.

IsSet IsSet IsSet IsSet

表示 CountdownEvent 对象的当前计数是否已归零。Indicates whether the CountdownEvent object's current count has reached zero.

WaitHandle WaitHandle WaitHandle WaitHandle

获取用于等待要设置的事件的 WaitHandleGets a WaitHandle that is used to wait for the event to be set.

方法

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

CountdownEvent 的当前计数加 1。Increments the CountdownEvent's current count by one.

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

CountdownEvent 的当前计数增加指定值。Increments the CountdownEvent's current count by a specified value.

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

释放 CountdownEvent 类的当前实例所使用的所有资源。Releases all resources used by the current instance of the CountdownEvent class.

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

释放由 CountdownEvent 占用的非托管资源,还可以另外再释放托管资源。Releases the unmanaged resources used by the CountdownEvent, and optionally releases the managed resources.

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

确定指定的对象是否等于当前对象。Determines whether the specified object is equal to the current object.

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

作为默认哈希函数。Serves as the default hash function.

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

获取当前实例的 TypeGets the Type of the current instance.

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

创建当前 Object 的浅表副本。Creates a shallow copy of the current Object.

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

CurrentCount 重置为 InitialCount 的值。Resets the CurrentCount to the value of InitialCount.

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

InitialCount 属性重新设置为指定值。Resets the InitialCount property to a specified value.

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

CountdownEvent 注册信号,同时减小 CurrentCount 的值。Registers a signal with the CountdownEvent, decrementing the value of CurrentCount.

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

CountdownEvent 注册多个信号,同时将 CurrentCount 的值减少指定数量。Registers multiple signals with the CountdownEvent, decrementing the value of CurrentCount by the specified amount.

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

返回表示当前对象的字符串。Returns a string that represents the current object.

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

增加一个 CurrentCount 的尝试。Attempts to increment CurrentCount by one.

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

增加指定值的 CurrentCount 的尝试。Attempts to increment CurrentCount by a specified value.

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

阻止当前线程,直到设置了 CountdownEvent 为止。Blocks the current thread until the CountdownEvent is set.

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

阻止当前线程,直到设置了 CountdownEvent 为止,同时观察 CancellationTokenBlocks the current thread until the CountdownEvent is set, while observing a CancellationToken.

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

阻止当前线程,直到设置了 CountdownEvent 为止,同时使用 32 位带符号整数测量超时。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)

阻止当前线程,直到设置了 CountdownEvent 为止,并使用 32 位带符号整数测量超时,同时观察 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)

阻止当前线程,直到设置了 CountdownEvent 为止,同时使用 TimeSpan 测量超时。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)

阻止当前线程,直到设置了 CountdownEvent 为止,并使用 TimeSpan 测量超时,同时观察 CancellationTokenBlocks the current thread until the CountdownEvent is set, using a TimeSpan to measure the timeout, while observing a CancellationToken.

适用于

线程安全性

所有公共和受保护成员CountdownEvent是线程安全的可同时从多个线程,除Dispose(),它必须仅当使用上的所有其他操作CountdownEvent已完成,和Reset(),其中应仅用于当没有其他线程同时访问该事件。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.

另请参阅