c# - Ok() 怎么可能既是 Task 又是 IActionResult？

Question

在 Controller 中在 .NET Core 中你可以返回 Ok()作为IActionResult .但我不明白它怎么还可以返回一个Task<IActionResult> .

例子:

    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()返回 OkResult ，它又实现了 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这个问题。异步方法隐式地将返回值“包装”在任务中。

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

对比

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