C# 非同步方法鏈式呼叫

原本是巢式呼叫

var asyncCalculator= new AsyncCalculator(0);
var asyncCalculateResult =
(
    await (
        await (
            await (
                await asyncCalculator.PlusAsync(1)
            ).MinusAsync(2)
        ).MultiplyAsync(3)
    ).DivideAsync(4)
).CalculateResult;

改寫成鏈式呼叫，一目瞭然

var asyncCalculator= new AsyncCalculator(0);
var asyncCalculateResult = await asyncCalculator.PlusAsync(1)
    .ContinueWith(t => t.GetAwaiter().GetResult().MinusAsync(2)).Unwrap()
    .ContinueWith(t => t.GetAwaiter().GetResult().MultiplyAsync(3)).Unwrap()
    .ContinueWith(t => t.GetAwaiter().GetResult().DivideAsync(4)).Unwrap()
    .ContinueWith(t => t.GetAwaiter().GetResult().CalculateResult);
//因為t.Result的異常會被包裝在AggregateException異常裡，所以改成呼叫t.GetAwaiter().GetResult()方法。
//與JavaScript不同，會再多包一層Task回傳，所以要用Unwrap()方法剝掉。