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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46
｜
第
3
章
可以在
System.Linq.Async
NuGet
包中找到可用于异步流的
LINQ
运算符。
若想了解更多可用于异步流的
LINQ
运算符，请参考
System.Interactive.
Async
NuGet
包。
参阅
3.5
节探讨创建异步流。
3.6
节探讨消耗异步流。
3.8
异步流及其取消操作
问题
假设需要取消异步流。应该怎么做呢？
解决方案
并非所有的异步流都需要取消。当满足条件时，简单地停止枚举也是可行的。如下例所
示，如果这种类型的“取消”可以满足需要，便不再需要真正意义上的取消操作：
await
foreach
(
int
result
in
SlowRange())
{
Console.WriteLine(result);
if
(result >= 8)
break
;
}
// 生成序列，该序列逐渐减缓
async
IAsyncEnumerable<
int
> SlowRange()
{
for
(
int
i = 0; i != 10; ++i)
{
await
Task.Delay(i * 100);
yield
return
i;
}
}
取消异步流往往是有用的，这是因为某些运算符会对它们的源流传递取消令牌。在这种场
景中，就要用
CancellationToken
从外部代码停止
await foreach
。
通过定义标记了
EnumeratorCancellation
属性的参数，返回
IAsyncEnumerable<T>
的
async
方法也许可以接受取消令牌。通过将令牌传递给其他 ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.