无法添加并行任务

2024-05-07 • 问答

如何为该代码添加任务并行性？我已经在几个地方添加了，但是它没有按预期运行。

class Program
{
    static void Main(string[] args)
    {
        Task.Run(() =>PizzaTask());
    }

    static async void PizzaTask()
    {
        Stopwatch stopwatch = new Stopwatch();
        stopwatch.Start();
        int totalPizza = 10;
        Console.WriteLine($"Started preparing {totalPizza} pizza");
        for (var x = 1; x <= totalPizza; x++)
        {
            //Task.Run(() => MakePizza(x));
            await MakePizza(x);
        }
        stopwatch.Stop();

        Console.WriteLine($"Finished preparing {totalPizza} pizza");
        Console.WriteLine("Elapsed time: " + stopwatch.Elapsed.TotalSeconds);

    }

    static async Task MakePizza(int n)
    {
        PreparePizza(n);
        await BakePizza(n);
    }

    static void PreparePizza(int n)
    {
        Console.WriteLine("Start preparing pizza " + n);
        Thread.Sleep(5000);// synchronous
        Console.WriteLine("Finished preparing pizza " + n);
    }

    static async Task BakePizza(int n)
    {
        Console.WriteLine("Start baking pizza " + n);
        await Task.Delay(15000); // asynchronous 
        //Thread.Sleep(15000); // synchronous 
        Console.WriteLine("Finished baking pizza " + n);
    }
}

之前的工作版本在BakePizza中，我设置为异步等待。但是，如果我为PizzaTask（）设置了异步等待，则无法正常工作。

我已经更改了代码，以使其通过var tasks = Enumerable.Range(0,totalPizza).Select(i => MakePizza(i));使用并行循环进行异步操作

下面的代码并行调用MakePizza，而不是通过for (var x = 1; x <= totalPizza; x++) { //Task.Run(() => MakePizza(x)); await MakePizza(x); }
使用Task.Delay而非Thread.Sleep来确保当前线程未被阻止。
将代码从async void更改为aysnc Task。 async+void组合可能会使系统崩溃，通常只应在UI端事件处理程序上使用。
如@Steve所述，请使用ConfigureAwait(false)返回任何可用线程，而不是强制上下文返回调用者线程。

更新代码：

public class Program
{
    public static void Main()
    {
       PizzaTask().GetAwaiter().GetResult();
    }

    static async Task PizzaTask()
    {
        Stopwatch stopwatch = new Stopwatch();
        stopwatch.Start();
        int totalPizza = 10;
        Console.WriteLine("Started preparing " + totalPizza + "  pizza");

        var tasks = Enumerable.Range(0,totalPizza).Select(i => MakePizza(i));
        await Task.WhenAll(tasks).ConfigureAwait(false);

        stopwatch.Stop();

        Console.WriteLine("Finished preparing " + totalPizza + "  pizza");
        Console.WriteLine("Elapsed time: " + stopwatch.Elapsed.TotalSeconds);

    }

    static async Task MakePizza(int n)
    {
        await PreparePizza(n).ConfigureAwait(false);
        await BakePizza(n).ConfigureAwait(false);
    }

    static async Task PreparePizza(int n)
    {
        Console.WriteLine("Start preparing pizza " + n);
        await Task.Delay(5000);
        //Thread.Sleep(5000);// synchronous
        Console.WriteLine("Finished preparing pizza " + n);
    }

    static async Task BakePizza(int n)
    {
        Console.WriteLine("Start baking pizza " + n);
        await Task.Delay(15000); // asynchronous 
        //Thread.Sleep(15000); // synchronous 
        Console.WriteLine("Finished baking pizza " + n);
    }
}

您可以在dotnetfiddle中检查代码的输出-https://dotnetfiddle.net/HepavC

无法添加并行任务

zwj1590971 回答：无法添加并行任务

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