如何将返回非泛型Task的函数转换为ValueTask? [英] How should I convert a function returning a non-generic Task to ValueTask?

问题描述

我正在研究一些代码，该代码在内存中建立一个缓冲区，然后在缓冲区填满时将其清空为 TextWriter .大多数情况下，角色会(同步)直接进入缓冲区，但偶尔(每4kb一次)我需要调用 TextWriter.WriteAsync .

I'm working on some code which builds a buffer in memory and then empties it into a TextWriter when the buffer fills up. Most of the time, the character will go straight into the buffer (synchronously) but occasionally (once every 4kb) I need to call TextWriter.WriteAsync.

在 System.Threading.Tasks.Extensions 中包中似乎只有一个 ValueTask< T> 结构，并且没有非通用的 ValueTask (无类型参数).为什么没有 ValueTask ，以及如果我需要转换返回非通用 Task (即，与void 方法)添加到 ValueTask ?

In the System.Threading.Tasks.Extensions package there only appears to be a ValueTask<T> struct, and no non-generic ValueTask (without a type parameter). Why is there no ValueTask, and what should I do if I need to convert a method returning a non-generic Task (that is, the async equivalent of a void method) to ValueTask?

推荐答案

在黑暗中射击，但是我认为这是因为

Shot in the dark, but I think it's because Task.CompletedTask is sufficient for most non-generic cases.

想到 ValueTask< T> 的一种方法是将 Task< T> 和 T 结合起来(对于异步和同步情况分别).因此，非通用的 ValueTask 将是 Task 的联合，并且……什么都没有，所以只是一个 Task .

One way to think of ValueTask<T> is as a union of Task<T> and T (for asynchronous and synchronous cases respectively). Accordingly a non-generic ValueTask would be a union of Task and... nothing, so just a Task.

我想不出非通用的 ValueTask 与缓存已完成的 Task (这是 Task)实际上不同的情况.CompletedTask 是)，尽管我很想学习任何内容.

I can't think of a case where a non-generic ValueTask would be practically different than caching an already completed Task (which is what Task.CompletedTask is), though I'd love to learn about any.

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