Ok（）如何同时是Task <iactionresult>和IActionResult？

Question

在.NET Core的Controller中，您可以Ok()作为IActionResult返回。但我不明白它如何也能返回Task<IActionResult>。

示例：

    public class FooController : Controller
    {

        [HttpGet]
        public async Task<IActionResult> OkResultAsync()
        {
            // This is ok. But I don't get why since OkResult != Task<IActionResult>
            OkResult result = Ok();
            return result;
        }

        [HttpGet]
        public IActionResult OkResult()
        {
            // This is ok, and it seems logical since OkResult implements IActionResult.
            OkResult result = Ok();
            return result;
        }

        [HttpGet]
        public FooResult Bar()
        {
            // This is ok.
            return new FooResult();
        }

        [HttpGet] 
        public async Task<FooResult> BarAsync()
        {
            // This is not ok since FooResult != Task<FooResult>
            return new FooResult();
        }
    }

Ok()会返回OkResult，而会生成IActionResult。如果方法签名返回Task<IActionResult>，.NET如何知道如何处理它（无需等待？）

Answer 1

async关键字使编译器自动处理此问题。隐式的异步方法＆＃34; wrap＆＃34;任务中的返回值。

async Task<int> GetNumber()
{
    return 42;
}

VS

Task<int> GetNumber()
{
    return Task.FromResult(42);
}

Answer 2

async关键字是一种在Task中包装方法内容的简写。当您在异步方法内部返回时，编译器会将其包装到您的任务中。例如，这两种方法基本相同：

private static Task<string> Hello()
{
    return new Task<string>(() => "hello");
} 

private static async Task<string> AsyncHello()
{
    return "hello";
}