遇到await后，后序代码由新线程接管，即操作开始异步。 官方文档
简易版
不阻塞主线程
class Program
{
static void Main(string[] args)
{
Console.WriteLine($"主线程{Thread.CurrentThread.ManagedThreadId}");
Console.WriteLine($"主线程{Thread.CurrentThread.ManagedThreadId}:{SayAsync().Status}");
Console.WriteLine($"主线程{Thread.CurrentThread.ManagedThreadId}");
Console.ReadKey(true);
}
public static async Task<string> SayAsync()
{
Console.WriteLine($"主线程{Thread.CurrentThread.ManagedThreadId}_SayAsync");
var s = await Task<string>.Run(async () =>
{
await Task.Delay(TimeSpan.FromSeconds(2));
Console.WriteLine("---------------两秒后----------------");
Console.WriteLine($"子线程{Thread.CurrentThread.ManagedThreadId}");
return "vvull";
});
Console.WriteLine($"子线程{Thread.CurrentThread.ManagedThreadId}:{s}");
Console.WriteLine($"子线程{Thread.CurrentThread.ManagedThreadId}");
return s;
}
}
阻塞主线程
class Program
{
static void Main(string[] args)
{
Console.WriteLine($"主线程{Thread.CurrentThread.ManagedThreadId}");
Console.WriteLine($"主线程{Thread.CurrentThread.ManagedThreadId}:{SayAsync().Result}");//阻塞主线程
Console.WriteLine($"主线程{Thread.CurrentThread.ManagedThreadId}");
Console.ReadKey(true);
}
public static async Task<string> SayAsync()
{
Console.WriteLine($"主线程{Thread.CurrentThread.ManagedThreadId}_SayAsync");
var s = await Task<string>.Run(async () =>
{
await Task.Delay(TimeSpan.FromSeconds(2));
Console.WriteLine("---------------两秒后----------------");
Console.WriteLine($"子线程{Thread.CurrentThread.ManagedThreadId}");
return "vvull";
});
Console.WriteLine($"子线程{Thread.CurrentThread.ManagedThreadId}:{s}");
Console.WriteLine($"子线程{Thread.CurrentThread.ManagedThreadId}");
return s;
}
}
进阶版
class Program
{
static void Main(string[] args)
{
Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->主线程");
giaoAsync();
Thread.Sleep(3000);
Console.WriteLine("---------------三秒后----------------");
Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->主线程");
Console.ReadKey();
}
static async Task giaoAsync()
{
Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->giao");
//Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->giao:{await SayAsync()}");//本句以后由新线程接管
//Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->giao*");
var s = await SayAsync();//由新线程接管
Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->giao**_{s}");
Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->giao**");
var ss = await SayAsync();//由新线程接管
Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->giao***_{ss}");
Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->giao***");
}
public static async Task<string> SayAsync()
{
Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->SayAsync");
var s = await Task<string>.Run(async () =>
{
Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->SayAsync*");
await Task.Delay(TimeSpan.FromSeconds(2));
Console.WriteLine("---------------两秒后----------------");
Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->SayAsync**");
return "vvull";
});
Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->SayAsync**_{s}");
Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->SayAsync**");
return s;
}
}
官方例子魔改
using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
namespace AsyncBreakfast
{
class Program
{
static async Task Main(string[] args)
{
Coffee cup = PourCoffee();
Console.WriteLine("coffee is ready");
Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->线程*");
var eggsTask = FryEggsAsync(2);
var baconTask = FryBaconAsync(3);
var toastTask = MakeToastWithButterAndJamAsync(2);
Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->线程*");
var breakfastTasks = new List<Task> { eggsTask, baconTask, toastTask };
while (breakfastTasks.Count > 0)
{
Task finishedTask = await Task.WhenAny(breakfastTasks);
Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->线程**");
if (finishedTask == eggsTask)
{
Console.WriteLine("eggs are ready");
}
else if (finishedTask == baconTask)
{
Console.WriteLine("bacon is ready");
}
else if (finishedTask == toastTask)
{
Console.WriteLine("toast is ready");
}
breakfastTasks.Remove(finishedTask);
Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->线程**");
}
Juice oj = PourOJ();
Console.WriteLine("oj is ready");
Console.WriteLine("Breakfast is ready!");
Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->线程***");
Console.ReadKey();
}
static async Task<Toast> MakeToastWithButterAndJamAsync(int number)
{
Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->线程*");
var toast = await ToastBreadAsync(number);
Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->Toast线程");
ApplyButter(toast);
ApplyJam(toast);
return toast;
}
private static Juice PourOJ()
{
Console.WriteLine("Pouring orange juice");
return new Juice();
}
private static void ApplyJam(Toast toast) =>
Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->Toast线程 " + "Putting jam on the toast");
private static void ApplyButter(Toast toast) =>
Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->Toast线程 " + "Putting butter on the toast");
private static async Task<Toast> ToastBreadAsync(int slices)
{
Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->线程*");
for (int slice = 0; slice < slices; slice++)
{
Console.WriteLine("Putting a slice of bread in the toaster");
}
Console.WriteLine("Start toasting...");
await Task.Delay(3000);
Console.WriteLine("--------Toast三秒后--------");
Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->Toast线程");
Console.WriteLine("Remove toast from toaster");
return new Toast();
}
private static async Task<Bacon> FryBaconAsync(int slices)
{
Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->线程*");
Console.WriteLine($"putting {slices} slices of bacon in the pan");
Console.WriteLine("cooking first side of bacon...");
await Task.Delay(3000);
Console.WriteLine("--------Bacon三秒后--------");
for (int slice = 0; slice < slices; slice++)
{
Console.WriteLine("flipping a slice of bacon");
}
Console.WriteLine("cooking the second side of bacon...");
Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->Bacon线程*");
await Task.Delay(3000);
Console.WriteLine("--------Bacon第二次三秒后--------");
Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->Bacon线程**");
Console.WriteLine("Put bacon on plate");
return new Bacon();
}
private static async Task<Egg> FryEggsAsync(int howMany)
{
Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->线程*");
Console.WriteLine("Warming the egg pan...");
await Task.Delay(3000);
Console.WriteLine("--------Eggs三秒后--------");
Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->Eggs线程*");
Console.WriteLine($"cracking {howMany} eggs");
Console.WriteLine("cooking the eggs ...");
await Task.Delay(3000);
Console.WriteLine("--------Eggs第二次三秒后--------");
Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}->Eggs线程**");
Console.WriteLine("Put eggs on plate");
return new Egg();
}
private static Coffee PourCoffee()
{
Console.WriteLine("Pouring coffee");
return new Coffee();
}
}
class Egg
{
}
class Toast
{
}
class Juice
{
}
class Bacon
{
}
class Coffee
{
}
}
