CancellationToken.IsCancellationRequested 属性
定义
重要
一些信息与预发行产品相关，相应产品在发行之前可能会进行重大修改。 对于此处提供的信息，Microsoft 不作任何明示或暗示的担保。
获取是否已请求取消此标记。
public:
property bool IsCancellationRequested { bool get(); };public bool IsCancellationRequested { get; }member this.IsCancellationRequested : boolPublic ReadOnly Property IsCancellationRequested As Boolean属性值
如果此令牌已请求取消，则为 true；否则为 false。
示例
下面是执行服务器进程的简单示例，直到 IsCancellationRequested 属性返回 true。
using System;
using System.Threading;
public class ServerClass
{
public static void StaticMethod(object obj)
{
CancellationToken ct = (CancellationToken)obj;
Console.WriteLine("ServerClass.StaticMethod is running on another thread.");
// Simulate work that can be canceled.
while (!ct.IsCancellationRequested) {
Thread.SpinWait(50000);
}
Console.WriteLine("The worker thread has been canceled. Press any key to exit.");
Console.ReadKey(true);
}
}
public class Simple
{
public static void Main()
{
// The Simple class controls access to the token source.
CancellationTokenSource cts = new CancellationTokenSource();
Console.WriteLine("Press 'C' to terminate the application...\n");
// Allow the UI thread to capture the token source, so that it
// can issue the cancel command.
Thread t1 = new Thread(() => { if (Console.ReadKey(true).KeyChar.ToString().ToUpperInvariant() == "C")
cts.Cancel(); } );
// ServerClass sees only the token, not the token source.
Thread t2 = new Thread(new ParameterizedThreadStart(ServerClass.StaticMethod));
// Start the UI thread.
t1.Start();
// Start the worker thread and pass it the token.
t2.Start(cts.Token);
t2.Join();
cts.Dispose();
}
}
// The example displays the following output:
// Press 'C' to terminate the application...
//
// ServerClass.StaticMethod is running on another thread.
// The worker thread has been canceled. Press any key to exit.
Imports System.Threading
Public Class ServerClass
Public Shared Sub StaticMethod(obj As Object)
Dim ct AS CancellationToken = CType(obj, CancellationToken)
Console.WriteLine("ServerClass.StaticMethod is running on another thread.")
' Simulate work that can be canceled.
While Not ct.IsCancellationRequested
Thread.SpinWait(50000)
End While
Console.WriteLine("The worker thread has been canceled. Press any key to exit.")
Console.ReadKey(True)
End Sub
End Class
Public Class Simple
Public Shared Sub Main()
' The Simple class controls access to the token source.
Dim cts As New CancellationTokenSource()
Console.WriteLine("Press 'C' to terminate the application..." + vbCrLf)
' Allow the UI thread to capture the token source, so that it
' can issue the cancel command.
Dim t1 As New Thread( Sub()
If Console.ReadKey(true).KeyChar.ToString().ToUpperInvariant() = "C" Then
cts.Cancel()
End If
End Sub)
' ServerClass sees only the token, not the token source.
Dim t2 As New Thread(New ParameterizedThreadStart(AddressOf ServerClass.StaticMethod))
' Start the UI thread.
t1.Start()
' Start the worker thread and pass it the token.
t2.Start(cts.Token)
t2.Join()
cts.Dispose()
End Sub
End Class
' The example displays the following output:
' Press 'C' to terminate the application...
'
' ServerClass.StaticMethod is running on another thread.
' The worker thread has been canceled. Press any key to exit.
该示例实例化一个 CancellationTokenSource 对象，该对象控制对取消令牌的访问。 然后定义两个线程过程。 第一个表达式定义为池键盘的 lambda 表达式，当按下“C”键时，调用 CancellationTokenSource.Cancel 将取消令牌设置为已取消状态。 第二个是参数化方法，ServerClass.StaticMethod在属性为true前IsCancellationRequested执行循环。
然后，主线程启动两个线程并阻止，直到执行该方法的 ServerClass.StaticMethod 线程终止。
注解
此属性指示是否已为此令牌请求取消，要么是通过最初在取消状态下构造的令牌，还是通过调用 Cancel 令牌的关联 CancellationTokenSource来构造。
如果此属性为 true此属性，则仅保证已请求取消。 它不能保证每个已注册的处理程序都已完成执行，也不能保证取消请求已完成传播到所有已注册处理程序。 可能需要其他同步，尤其是在同时取消相关对象的情况下。