Async和Await

public class AwaitAsyncShow
{
public static void Show()
{
Test();
}
private async static Task Test()
{
Console.WriteLine($"当前主线程id={Thread.CurrentThread.ManagedThreadId}");
{
//NoReturnNoAwait();
}
{
//NoReturn();
//for (int i = 0; i < 10; i++)
//{
// Thread.Sleep(300);
// Console.WriteLine($"Main Thread Task ManagedThreadId={Thread.CurrentThread.ManagedThreadId} i={i}");
//}
}
{
//Task t = NoReturnTask();
//Console.WriteLine($"Main Thread Task ManagedThreadId={Thread.CurrentThread.ManagedThreadId}");
//t.Wait();//主线程等待Task的完成
//await t;//await后的代码会由 子线程执行
}
{
Task<long> t = SumAsync();
Console.WriteLine($"Main Thread Task ManagedThreadId={Thread.CurrentThread.ManagedThreadId}");
long lResult = t.Result;//访问result 主线程等待Task的完成
t.Wait();//等价于上一行
}

Console.Read();
}

/// <summary>
/// 只有async没有await，会有个warn
/// 跟普通方法没有区别
/// </summary>
private static async void NoReturnNoAwait()
{
//主线程执行
Console.WriteLine($"NoReturnNoAwait Sleep before Task,ThreadId={Thread.CurrentThread.ManagedThreadId}");
Task task = Task.Run(() =>
{
Console.WriteLine($"NoReturnNoAwait Sleep before,ThreadId={Thread.CurrentThread.ManagedThreadId}");
Thread.Sleep(3000);
Console.WriteLine($"NoReturnNoAwait Sleep after,ThreadId={Thread.CurrentThread.ManagedThreadId}");
});

//主线程执行
Console.WriteLine($"NoReturnNoAwait Sleep after Task,ThreadId={Thread.CurrentThread.ManagedThreadId}");
}

/// <summary>
/// async/await
/// 不能单独await
/// await只能放在task前面
/// 不推荐void返回值，使用Task来代替
/// Task和Task<T>能够使用await，Task.WhenAny，Task.WhenAll等方式组合使用。Async Void 不行
/// </summary>
private static async void NoReturn()
{
//主线程执行
Console.WriteLine($"NoReturn Sleep before await,ThreadId={Thread.CurrentThread.ManagedThreadId}");
TaskFactory taskFactory = new TaskFactory();
Task task = taskFactory.StartNew(() =>
{
Console.WriteLine($"NoReturn Sleep before,ThreadId={Thread.CurrentThread.ManagedThreadId}");
Thread.Sleep(3000);
Console.WriteLine($"NoReturn Sleep after,ThreadId={Thread.CurrentThread.ManagedThreadId}");
});
await task;//主线程在这里就返回来，执行主线程任务去了

//耗时任务就用await

//子线程执行 其实是封装成委托，在task之后成为回调（编译器功能，状态机实现）
//task.ContinueWith()
//这个回调的线程是不确定的：可能是主线程，可能是子线程，也可能是其他线程
Console.WriteLine($"NoReturn Sleep after Task,ThreadId={Thread.CurrentThread.ManagedThreadId}");
}

/// <summary>
/// 无返回值 async Task==async void
/// Task和Task<T>能够使用await，Task.WhenAny,Task.WhenAll等方式组合使用。Async void不行
/// </summary>
/// <returns></returns>
private static async Task NoReturnTask()
{
//这里是主线程的Id
Console.WriteLine($"NoReturnTask Sleep before await,ThreadId={Thread.CurrentThread.ManagedThreadId}");
await Task.Run(() =>
{
Console.WriteLine($"NoReturnTask Sleep before,ThreadId={Thread.CurrentThread.ManagedThreadId}");
Thread.Sleep(3000);
Console.WriteLine($"NoReturnTask Sleep after,ThreadId={Thread.CurrentThread.ManagedThreadId}");
});
//await task
Console.WriteLine($"NoReturnTask Sleep after await,ThreadId={Thread.CurrentThread.ManagedThreadId}");

//return new TaskFactory().StartNew(() => { });//不能return 没有async才行
}

/// <summary>
/// 待返回至的Task 要使用返回值就一定要等到子线程计算完毕
/// </summary>
/// <returns></returns>
private static async Task<long> SumAsync()
{
Console.WriteLine($"SumAsync 111 start ManagedThreadId={Thread.CurrentThread.ManagedThreadId}");
long result = 0;

await Task.Run(() =>
{
for (int i = 0; i < 10; i++)
{
Console.WriteLine(
$"SumAsync {i} await Task.Run ManagedThreadId={Thread.CurrentThread.ManagedThreadId}");
Thread.Sleep(1000);
}

for (long k = 0; k < 999999999; k++)
{
result += k;
}
});
Console.WriteLine($"SumFactory 111 end ManagedThreadId={Thread.CurrentThread.ManagedThreadId}");
return result;
}

/// <summary>
/// 真的返回Task 不是async 要使用返回值就一定要等子线程计算完毕
/// </summary>
/// <returns></returns>
private static Task<int> SumFactory()
{
Console.WriteLine($"SumFactory 111 start ManagedThreadId={Thread.CurrentThread.ManagedThreadId}");
TaskFactory taskFactory=new TaskFactory();
Task<int> iResult= taskFactory.StartNew<int>(() =>
{
Thread.Sleep(3000);
Console.WriteLine(
$"SumFactory 123 Task.Run ManagedThreadId={Thread.CurrentThread.ManagedThreadId}");

return 123;
});
Console.WriteLine($"SumFactory 111 end ManagedThreadId={Thread.CurrentThread.ManagedThreadId}");
return iResult;
}
}