异步创建方法运行

Question

谁能看看这段代码并告诉我我做错了什么。在我看来，这3个方法应该运行相同，但它们一个接一个运行。请查看控制台上写的时间。在我看来，所有 Console.WriteLine 都应该显示 ~60ms。下面的代码示例：

private async void GetOneCombination(string firstMarket, string secondMarket, string thirdMarket, decimal amountOfFirstCurrency)
    {
        Stopwatch sw = new Stopwatch();
        sw.Start();

        Task<GetMarketResponse> result = _accessMethods.GetOrderbook(firstMarket);
        Console.WriteLine(sw.ElapsedMilliseconds); // ~60ms
        Task<GetMarketResponse> result1 = _accessMethods.GetOrderbook(secondMarket);
        Console.WriteLine(sw.ElapsedMilliseconds); // ~130 ms
        Task<GetMarketResponse> result2 = _accessMethods.GetOrderbook(thirdMarket);
        Console.WriteLine(sw.ElapsedMilliseconds); // ~200 ms
        var getMarketResponses = await Task.WhenAll(result, result1, result2);

    }

编辑：老实说，我认为这个方法里面有什么并不重要，我认为无论里面做什么，它都会同时完成 3 次

  public async Task<GetMarketResponse> GetOrderbook(string market = "USD")
    {
        var address = AddressBook._orderbook + market;
        var response = MethodExecutionTimeMeasurer.Invoke(() => 
            _client.ExecuteGetAsyncPublic<GetMarketResponse>(address), out timespan);
        _logger.LogInformation(string.Format("OrderBook requested for [{0}], response message: {1}. Time[ms]:{2}", 
            address, 
            response.Status,
            timespan));
        return response; 
    }

和 ExecuteGetAsyncPublic：

   public async Task<T> ExecuteGetAsyncPublic<T>(string method)
        where T : IBasicResponse
    {
        var response = await _httpClient.GetAsync(method).ConfigureAwait(false);
        response.EnsureSuccessStatusCode();
        var json = await response.Content.ReadAsStringAsync();
        var responseData = JsonConvert.DeserializeObject<T>(json);
        return responseData;
    }

MethodExecutionTimeMeasurer

public static class MethodExecutionTimeMeasurer
{
    public static T Invoke<T>(Func<Task<T>> action, out TimeSpan timeSpan)
    {
        var timer = Stopwatch.StartNew();
        var res = action.Invoke();
        res.Wait();
        timer.Stop();
        timeSpan = timer.Elapsed;
        return res.Result;
    }

    public static void Invoke(Action action, out TimeSpan timeSpan)
    {
        var timer = Stopwatch.StartNew();
        action.Invoke();
        timer.Stop();
        timeSpan = timer.Elapsed;
    }
}

Answer 1

这里有两个问题：

GetOrderbook 方法具有异步签名，但其实现是同步的。您可能收到 async 方法缺少 await 运算符的警告。
MethodExecutionTimeMeasurer.Invoke有一个参数Func<Task<T>> action（异步委托），但是创建的Task是和Wait方法同步等待的。所以在任务执行过程中，当前线程是阻塞的。

三个_accessMethods.GetOrderbook调用中的每一个returns一个完成的任务，然后组合任务Task.WhenAll(result, result1, result2)也在创建时完成，简而言之，从当前线程的角度来看，没有什么是运行 a同步。此案例与昨天提出的问题非常相似，。

Answer 2

调用异步任务方法不会立即在新线程上启动。它将运行在它被调用的线程上，直到遇到等待。

so for example
var task = DoSomething();

public async Task DoSomething()
{
    // MAIN THREAD

    await Task.Delay(1);

    // WORKER THREAD

}

如果你这样做它可能会奏效

 public async Task<GetMarketResponse> GetOrderbook(string market = "USD")
    {
        await Task.Delay(1);
        var address = AddressBook._orderbook + market;
        var response = MethodExecutionTimeMeasurer.Invoke(() => 
            _client.ExecuteGetAsyncPublic<GetMarketResponse>(address), out timespan);
        _logger.LogInformation(string.Format("OrderBook requested for [{0}], response message: {1}. Time[ms]:{2}", 
            address, 
            response.Status,
            timespan));
        return response; 
    }

您可以采用的另一种方法是

Parallel.Invoke(
() => _accessMethods.GetOrderbook(firstMarket).Wait(),
() => _accessMethods.GetOrderbook(secondMarket).Wait(),
() => _accessMethods.GetOrderbook(thirdMarket).Wait(),
);

异步创建方法运行

Make methods run asynchronously

.net

c#

multithreading

asynchronous

task

异步创建方法 运行

Make methods run asynchronously

.net

c#

multithreading

asynchronous

task

异步创建方法运行