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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讨论
这是一个简单的方法，但经常被忽视。通过使用
Task.Run
，可以把所有的并行处理推进线
程池中。
Task.Run
返回的
Task
代表了并行工作，而
UI
线程可以异步等待其完成。
该方法只适用于
UI
代码。以服务器端为例，比如
ASP.NET
，因为服务器已经有并行机制
了，所以它很少执行并行处理。因此，服务器端的代码既不应执行并行处理，也不应将工
作推进线程池中。
参阅
第
2
章探讨异步编程基础。
第
4
章探讨并行编程基础。
8.5
异步包装
System.Reactive
可观察对象
问题
假设有可观察流，需要用
await
来消耗。
解决方案
在详细研究解决方案之前，需要决定重点关注事件流中的哪些可观察事件，通常分为下面
3
种情况。
•
重点关注流结束前的最后一个事件。
•
重点关注下一个事件。
•
重点关注所有事件。
若要捕获流中的最后一个事件，可以对
LastAsync
的结果执行
await
或者直接用
await
等
待可观察对象：
IObservable<
int
> observable = ...;
int
lastElement =
await
observable.LastAsync();
// 或者用int lastElement = await observable;
当针对可观察对象或
LastAsync
执行
await
时，代码异步地等待，直到流完成，然后返回
最后的元素。其实在这个过程中，
await
也会订阅流。
若要捕获流中的下一个事件，可以使用
FirstAsync
。在下面的代码中，
await
订阅了流，
然后在第一个事件到达时，便立即完成（并取消订阅） ...
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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.