CancellationToken 構造体
定義
操作を取り消す通知を配信します。Propagates notification that operations should be canceled.
public value class CancellationTokenpublic struct CancellationToken[System.Runtime.InteropServices.ComVisible(false)]
public struct CancellationTokentype CancellationToken = struct[<System.Runtime.InteropServices.ComVisible(false)>]
type CancellationToken = structPublic Structure CancellationToken- 継承
- 属性
例
次の例では、乱数ジェネレーターを使用して、11個の異なる音色から10個の整数値を読み取るデータコレクションアプリケーションをエミュレートします。The following example uses a random number generator to emulate a data collection application that reads 10 integral values from eleven different instruments. 値が0の場合は、測定が1つの音色で失敗したことを示します。この場合、操作はキャンセルされ、全体的な平均は計算されません。A value of zero indicates that the measurement has failed for one instrument, in which case the operation should be cancelled and no overall mean should be computed.
この例では、操作の取り消しを処理するために、 CancellationTokenSource オブジェクトに渡されるキャンセルトークンを生成するオブジェクトをインスタンス化し TaskFactory ます。To handle the possible cancellation of the operation, the example instantiates a CancellationTokenSource object that generates a cancellation token that's passed to a TaskFactory object. さらに、オブジェクトは、 TaskFactory 特定のインストルメントの読み取りを収集する各タスクにキャンセルトークンを渡します。In turn, the TaskFactory object passes the cancellation token to each of the tasks responsible for collecting readings for a particular instrument. この TaskFactory.ContinueWhenAll<TAntecedentResult,TResult>(Task<TAntecedentResult>[], Func<Task<TAntecedentResult>[],TResult>, CancellationToken) メソッドは、すべての読み取りが正常に収集された後にのみ平均が計算されるようにするために呼び出されます。The TaskFactory.ContinueWhenAll<TAntecedentResult,TResult>(Task<TAntecedentResult>[], Func<Task<TAntecedentResult>[],TResult>, CancellationToken) method is called to ensure that the mean is computed only after all readings have been gathered successfully. タスクが取り消されたために完了しなかった場合、 TaskFactory.ContinueWhenAll メソッドは例外をスローします。If a task has not completed because it was cancelled, the TaskFactory.ContinueWhenAll method throws an exception.
using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
public class Example
{
public static void Main()
{
// Define the cancellation token.
CancellationTokenSource source = new CancellationTokenSource();
CancellationToken token = source.Token;
Random rnd = new Random();
Object lockObj = new Object();
List<Task<int[]>> tasks = new List<Task<int[]>>();
TaskFactory factory = new TaskFactory(token);
for (int taskCtr = 0; taskCtr <= 10; taskCtr++) {
int iteration = taskCtr + 1;
tasks.Add(factory.StartNew( () => {
int value;
int[] values = new int[10];
for (int ctr = 1; ctr <= 10; ctr++) {
lock (lockObj) {
value = rnd.Next(0,101);
}
if (value == 0) {
source.Cancel();
Console.WriteLine("Cancelling at task {0}", iteration);
break;
}
values[ctr-1] = value;
}
return values;
}, token));
}
try {
Task<double> fTask = factory.ContinueWhenAll(tasks.ToArray(),
(results) => {
Console.WriteLine("Calculating overall mean...");
long sum = 0;
int n = 0;
foreach (var t in results) {
foreach (var r in t.Result) {
sum += r;
n++;
}
}
return sum/(double) n;
} , token);
Console.WriteLine("The mean is {0}.", fTask.Result);
}
catch (AggregateException ae) {
foreach (Exception e in ae.InnerExceptions) {
if (e is TaskCanceledException)
Console.WriteLine("Unable to compute mean: {0}",
((TaskCanceledException) e).Message);
else
Console.WriteLine("Exception: " + e.GetType().Name);
}
}
finally {
source.Dispose();
}
}
}
// Repeated execution of the example produces output like the following:
// Cancelling at task 5
// Unable to compute mean: A task was canceled.
//
// Cancelling at task 10
// Unable to compute mean: A task was canceled.
//
// Calculating overall mean...
// The mean is 5.29545454545455.
//
// Cancelling at task 4
// Unable to compute mean: A task was canceled.
//
// Cancelling at task 5
// Unable to compute mean: A task was canceled.
//
// Cancelling at task 6
// Unable to compute mean: A task was canceled.
//
// Calculating overall mean...
// The mean is 4.97363636363636.
//
// Cancelling at task 4
// Unable to compute mean: A task was canceled.
//
// Cancelling at task 5
// Unable to compute mean: A task was canceled.
//
// Cancelling at task 4
// Unable to compute mean: A task was canceled.
//
// Calculating overall mean...
// The mean is 4.86545454545455.
Imports System.Collections.Generic
Imports System.Threading
Imports System.Threading.Tasks
Module Example
Public Sub Main()
' Define the cancellation token.
Dim source As New CancellationTokenSource()
Dim token As CancellationToken = source.Token
Dim lockObj As New Object()
Dim rnd As New Random
Dim tasks As New List(Of Task(Of Integer()))
Dim factory As New TaskFactory(token)
For taskCtr As Integer = 0 To 10
Dim iteration As Integer = taskCtr + 1
tasks.Add(factory.StartNew(Function()
Dim value, values(9) As Integer
For ctr As Integer = 1 To 10
SyncLock lockObj
value = rnd.Next(0,101)
End SyncLock
If value = 0 Then
source.Cancel
Console.WriteLine("Cancelling at task {0}", iteration)
Exit For
End If
values(ctr-1) = value
Next
Return values
End Function, token))
Next
Try
Dim fTask As Task(Of Double) = factory.ContinueWhenAll(tasks.ToArray(),
Function(results)
Console.WriteLine("Calculating overall mean...")
Dim sum As Long
Dim n As Integer
For Each t In results
For Each r In t.Result
sum += r
n+= 1
Next
Next
Return sum/n
End Function, token)
Console.WriteLine("The mean is {0}.", fTask.Result)
Catch ae As AggregateException
For Each e In ae.InnerExceptions
If TypeOf e Is TaskCanceledException
Console.WriteLine("Unable to compute mean: {0}",
CType(e, TaskCanceledException).Message)
Else
Console.WriteLine("Exception: " + e.GetType().Name)
End If
Next
Finally
source.Dispose()
End Try
End Sub
End Module
' Repeated execution of the example produces output like the following:
' Cancelling at task 5
' Unable to compute mean: A task was canceled.
'
' Cancelling at task 10
' Unable to compute mean: A task was canceled.
'
' Calculating overall mean...
' The mean is 5.29545454545455.
'
' Cancelling at task 4
' Unable to compute mean: A task was canceled.
'
' Cancelling at task 5
' Unable to compute mean: A task was canceled.
'
' Cancelling at task 6
' Unable to compute mean: A task was canceled.
'
' Calculating overall mean...
' The mean is 4.97363636363636.
'
' Cancelling at task 4
' Unable to compute mean: A task was canceled.
'
' Cancelling at task 5
' Unable to compute mean: A task was canceled.
'
' Cancelling at task 4
' Unable to compute mean: A task was canceled.
'
' Calculating overall mean...
' The mean is 4.86545454545455.
注釈
では、 CancellationToken スレッド、スレッドプール作業項目、またはオブジェクト間の協調的な取り消しが可能 Task です。A CancellationToken enables cooperative cancellation between threads, thread pool work items, or Task objects. キャンセルトークンを作成するには、オブジェクトをインスタンス化し CancellationTokenSource ます。このオブジェクトは、プロパティから取得されたキャンセルトークンを管理し CancellationTokenSource.Token ます。You create a cancellation token by instantiating a CancellationTokenSource object, which manages cancellation tokens retrieved from its CancellationTokenSource.Token property. 次に、キャンセルの通知を受け取る必要がある任意の数のスレッド、タスク、または操作にキャンセルトークンを渡します。You then pass the cancellation token to any number of threads, tasks, or operations that should receive notice of cancellation. トークンを使用してキャンセルを開始することはできません。The token cannot be used to initiate cancellation. 所有オブジェクトがを呼び出すと CancellationTokenSource.Cancel 、 IsCancellationRequested キャンセルトークンのすべてのコピーのプロパティがに設定され true ます。When the owning object calls CancellationTokenSource.Cancel, the IsCancellationRequested property on every copy of the cancellation token is set to true. 通知を受信するオブジェクトは、適切な方法で応答できます。The objects that receive the notification can respond in whatever manner is appropriate.
詳細とコード例については、「 マネージスレッドでのキャンセル」を参照してください。For more information and code examples see Cancellation in Managed Threads.
コンストラクター
| CancellationToken(Boolean) |
CancellationToken を初期化します。Initializes the CancellationToken. |
プロパティ
| CanBeCanceled |
このトークンが取り消された状態になることができるかどうかを取得します。Gets whether this token is capable of being in the canceled state. |
| IsCancellationRequested |
このトークンに対して取り消しが要求されたかどうかを取得します。Gets whether cancellation has been requested for this token. |
| None |
空の CancellationToken 値を返します。Returns an empty CancellationToken value. |
| WaitHandle |
トークンが取り消されたときに通知される WaitHandle を取得します。Gets a WaitHandle that is signaled when the token is canceled. |
メソッド
| Equals(CancellationToken) |
現在の CancellationToken インスタンスが指定されたトークンと等しいかどうかを判断します。Determines whether the current CancellationToken instance is equal to the specified token. |
| Equals(Object) |
現在の CancellationToken インスタンスが指定された Object と等しいかどうかを判断します。Determines whether the current CancellationToken instance is equal to the specified Object. |
| GetHashCode() |
CancellationToken のハッシュ関数として機能します。Serves as a hash function for a CancellationToken. |
| Register(Action) |
この CancellationToken が取り消されたときに呼び出されるデリゲートを登録します。Registers a delegate that will be called when this CancellationToken is canceled. |
| Register(Action, Boolean) |
この CancellationToken が取り消されたときに呼び出されるデリゲートを登録します。Registers a delegate that will be called when this CancellationToken is canceled. |
| Register(Action<Object>, Object) |
この CancellationToken が取り消されたときに呼び出されるデリゲートを登録します。Registers a delegate that will be called when this CancellationToken is canceled. |
| Register(Action<Object>, Object, Boolean) |
この CancellationToken が取り消されたときに呼び出されるデリゲートを登録します。Registers a delegate that will be called when this CancellationToken is canceled. |
| ThrowIfCancellationRequested() |
このトークンに対して取り消しが要求された場合、OperationCanceledException をスローします。Throws a OperationCanceledException if this token has had cancellation requested. |
| UnsafeRegister(Action<Object>, Object) |
この CancellationToken が取り消されたときに呼び出されるデリゲートを登録します。Registers a delegate that is called when this CancellationToken is canceled. |
演算子
| Equality(CancellationToken, CancellationToken) |
2 つの CancellationToken インスタンスが等しいかどうかを判断します。Determines whether two CancellationToken instances are equal. |
| Inequality(CancellationToken, CancellationToken) |
2 つの CancellationToken インスタンスが等しくないかどうかを判断します。Determines whether two CancellationToken instances are not equal. |
適用対象
スレッド セーフ
のすべてのパブリックメンバーとプロテクトメンバー CancellationToken はスレッドセーフであり、複数のスレッドから同時に使用できます。All public and protected members of CancellationToken are thread-safe and may be used concurrently from multiple threads.