c#异步编程-Task（一）

Task.Run(()=>{  Console.WriteLine("do it"); });

public enum TaskStatus
{
    //
    // 摘要:
    //     The task has been initialized but has not yet been scheduled.
    Created = 0,
    //
    // 摘要:
    //     The task is waiting to be activated and scheduled internally by the .NET Framework
    //     infrastructure.
    WaitingForActivation = 1,
    //
    // 摘要:
    //     The task has been scheduled for execution but has not yet begun executing.
    WaitingToRun = 2,
    //
    // 摘要:
    //     The task is running but has not yet completed.
    Running = 3,
    //
    // 摘要:
    //     The task has finished executing and is implicitly waiting for attached child
    //     tasks to complete.
    WaitingForChildrenToComplete = 4,
    //
    // 摘要:
    //     The task completed execution successfully.
    RanToCompletion = 5,
    //
    // 摘要:
    //     The task acknowledged cancellation by throwing an OperationCanceledException
    //     with its own CancellationToken while the token was in signaled state, or the
    //     task's CancellationToken was already signaled before the task started executing.
    //     For more information, see Task Cancellation.
    Canceled = 6,
    //
    // 摘要:
    //     The task completed due to an unhandled exception.
    Faulted = 7
}

if (task.Status == TaskStatus.RanToCompletion)
{
    //当当前线程状态表示完成时则执行后续操作
    Console.WriteLine("do it");
}

Task mytask = Task.Run(()=> 
{
    Thread.Sleep(3000);
    Console.WriteLine("do it");
});
Console.WriteLine(mytask.IsCanceled);//false
mytask.Wait();//阻塞主线程直到mytask执行完毕
Console.WriteLine(mytask.IsCanceled);//true

Task task = Task.Factory.StartNew(()=> 
{
    Thread.Sleep(3000);
    Console.WriteLine("do it");
},TaskCreationOptions.LongRunning);

Task mytask = Task.Run(()=> { throw null; });
try
{
    mytask.Wait();
}
catch (AggregateException aex)
{
    if (aex.InnerExceptions is NullReferenceException)
    {
        Console.WriteLine("null");
    }
    else
    {
        throw;
    }
}

    Task<int> mytask = Task.Run(() => 
    { 
        Console.WriteLine("do it");
        return 666;
    });
    var awaiter =  mytask.GetAwaiter();
    awaiter.OnCompleted(()=> 
    {
        int result = awaiter.GetResult();
        Console.WriteLine(result);
    });

Task<int> mytask = Task.Run(() => 
{ 
    Console.WriteLine("do it");
    return 666;
});
var awaiter =  mytask.ConfigureAwait(false).GetAwaiter();
awaiter.OnCompleted(()=> 
{
    int result = awaiter.GetResult();
    Console.WriteLine(result);
});

Task<int> mytask = Task.Run(() => 
{ 
    Console.WriteLine("do it");
    return 666;
});

mytask.ContinueWith(task=> 
{
    int result = task.Result;
    Console.WriteLine(result);
});

public class TaskCompletionSource<TResult>
{
    public TaskCompletionSource();

    public TaskCompletionSource(object? state);

    public TaskCompletionSource(TaskCreationOptions creationOptions);

    public TaskCompletionSource(object? state, TaskCreationOptions creationOptions);

    public Task<TResult> Task { get; }

    public void SetCanceled();

    public void SetException(IEnumerable<Exception> exceptions);

    public void SetException(Exception exception);

    public void SetResult(TResult result);

    public bool TrySetCanceled();

    public bool TrySetCanceled(CancellationToken cancellationToken);

    public bool TrySetException(IEnumerable<Exception> exceptions);

    public bool TrySetException(Exception exception);

    public bool TrySetResult(TResult result);
}

/*
 *CODE1
 */
var tcs = new TaskCompletionSource<int>();
new Thread(() =>
{
    Thread.Sleep(5000);
    tcs.SetResult(42);
})
{
    IsBackground = true
}.Start();

Task<int> task = tcs.Task;
Console.WriteLine(task.Result);


/*CODE2
 * 调用此方法相当于调用Task.Factory.StartNew
 * 并使用TaskCreationOptions.LongRunning选项来创建非线程池的线程
 */
Task<TResult> Run<TResult>(Func<TResult> func) 
{
    var tcs = new TaskCompletionSource<TResult>();
    new Thread(() =>
    {
        try
        {
            tcs.SetResult(func());
        }
        catch (Exception ex)
        {

            tcs.SetException(ex);
        }
    })
    {
        IsBackground = true
    }.Start();
    return tcs.Task;
}

static void Main(string[] args)
{
    //5秒钟之后，Continuation开始的时候，才占用线程
    Delay(5000).GetAwaiter().OnCompleted(() => Console.WriteLine(42));
    Console.ReadKey();
}

static Task Delay(int milliseconds) 
{
    var tcs = new TaskCompletionSource<object>();
    var timer = new System.Timers.Timer(milliseconds) { AutoReset = false };
    timer.Elapsed += delegate { timer.Dispose(); tcs.SetResult(null); };
    timer.Start();
    return tcs.Task;
}