November 2020
Intermediate to advanced
226 pages
5h 34m
Chinese
Content preview from C#并发编程经典实例（第2版）
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136
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第
10
章
cts.CancelAfter(TimeSpan.FromSeconds(5));
await
Task.Delay(TimeSpan.FromSeconds(10), token);
}
讨论
要通过超时来执行代码，请使用
CancellationTokenSource
和
CancelAfter
（或者构造器）。
其他方法也可以达到同样的目的，但现有的取消系统最简便，也最高效。
记住，有待取消的代码需要观察取消令牌。不可取消的代码是无法轻松取消的。
参阅
10.4
节探讨向
async
代码传递令牌。
10.5
节探讨向并行代码传递令牌。
10.6
节探讨在响应式代码中使用令牌。
10.7
节探讨向数据流网格传递令牌。
10.4
取消
async
代码
问题
假设正在使用的
async
代码需要支持取消。
解决方案
要在异步代码中支持取消，最简单的方法就是把
CancellationToken
传到下一层。下面的
示例代码执行了异步延迟，然后返回了值，通过向
Task.Delay
传递令牌来支持取消：
public async
Task<
int
> CancelableMethodAsync(CancellationToken cancellationToken)
{
await
Task.Delay(TimeSpan.FromSeconds(2), cancellationToken);
return
42;
}
因为许多异步
API
支持
CancellationToken
，所以实现取消通常只需要接受令牌，然后传
递它 ...
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