我是否应该担心“这种异步方法缺少 'await' 操作符并且将同步运行"?警告 [英] Should I worry about "This async method lacks 'await' operators and will run synchronously" warning

问题描述

我有一个公开一些异步方法的接口.更具体地说，它定义了返回 Task 或 Task 的方法.我正在使用 async/await 关键字.

I have a interface which exposes some async methods. More specifically it has methods defined which return either Task or Task<T>. I am using the async/await keywords.

我正在实现这个接口.但是，在其中一些方法中，此实现无需等待.出于这个原因，我收到编译器警告CS1998:此异步方法缺少 'await' 运算符，将同步运行......"

I am in the process of implementing this interface. However, in some of these methods this implementation doesn't have anything to await. For that reason I am getting the compiler warning "CS1998: This async method lacks 'await' operators and will run synchronously..."

我明白为什么我会收到这些警告，但我想知道在这种情况下我是否应该对它们做些什么.忽略编译器警告感觉不对.

I understand why I am getting these warnings but am wondering whether I should do anything about them in this context. It feels wrong to ignore compiler warnings.

我知道我可以通过等待 Task.Run 来修复它，但是对于只执行一些廉价操作的方法来说，这感觉是错误的.听起来它还会为执行增加不必要的开销，但我也不确定它是否已经存在，因为 async 关键字存在.

I know I can fix it by awaiting on Task.Run but that feels wrong for a method that is only doing a few inexpensive operations. It also sounds like it will add unneeded overhead to the execution but then I am also not sure if that is already there because the async keyword is present.

我应该忽略警告还是有办法解决我没有看到的问题?

Should I just ignore the warnings or is there a way of working around this that I am not seeing?

推荐答案

async 关键字只是一个方法的实现细节；它不是方法签名的一部分.如果一个特定的方法实现或覆盖没有什么可等待的，那么只需省略 async 关键字并使用 Task.FromResult:

The async keyword is merely an implementation detail of a method; it isn't part of the method signature. If one particular method implementation or override has nothing to await, then just omit the async keyword and return a completed task using Task.FromResult<TResult>:

public Task<string> Foo()               //    public async Task<string> Foo()
{                                       //    {
    Baz();                              //        Baz();
    return Task.FromResult("Hello");    //        return "Hello";
}                                       //    }

如果您的方法返回 TaskTask，那么你可以返回一个已完成的任务类型和值.Task.FromResult(0) 似乎是一个流行的选择:

If your method returns Task instead of Task<TResult>, then you can return a completed task of any type and value. Task.FromResult(0) seems to be a popular choice:

public Task Bar()                       //    public async Task Bar()
{                                       //    {
    Baz();                              //        Baz();
    return Task.FromResult(0);          //
}                                       //    }

或者，从 .NET Framework 4.6 开始，您可以返回 Task.CompletedTask:

Or, as of .NET Framework 4.6, you can return Task.CompletedTask:

public Task Bar()                       //    public async Task Bar()
{                                       //    {
    Baz();                              //        Baz();
    return Task.CompletedTask;          //
}                                       //    }

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