c# - 从类型为 void 的方法返回任务

Question

我想创建一个任务来运行串行命令。此时我不需要从执行工作的方法返回任何东西。这可能稍后会改变，但我现在很好奇这是怎么回事。

这是我的。我想为任务使用单独的方法而不是创建匿名操作。我试过返回 void，结果是“void cannot be explicitly converted to a Task”。我也试过了。 Task<void> .我尝试的最后一件事是返回一个任务，但我收到错误“并非所有代码路径都返回一个值”和“无法隐式地将 void 转换为类型任务”

过去我使用线程来完成此操作，但这次我想使用任务。

internal class Hardware
{
    private EventHandler<SequenceDoneEventArgs> SequenceDone;

    private List<Step> Steps;
    private System.IO.Ports.SerialPort comport = null;

    private Task SequenceTask;
    private CancellationTokenSource RequestStopSource;
    private CancellationToken RequestStopToken;


    private void Initialize()
    {
        comport = new System.IO.Ports.SerialPort("COM2", 115200, System.IO.Ports.Parity.None,8);
        comport.DataReceived += Comport_DataReceived;
    }

    public async void RunSequence()
    {
        if (comport == null)
        {
            Initialize();
        }
        if (!comport.IsOpen)
        {
            comport.Open();
        }

        RequestStopSource = new CancellationTokenSource();
        RequestStopToken = RequestStopSource.Token;

        SequenceTask = await Task.Run(() => { doSequence(); });

    }

    private Task doSequence()
    {
        //** Run Sequence stuff here

    }
}

预计到达时间:

最后这是我的完整解决方案

internal class Hardware
{
    private EventHandler<SequenceDoneEventArgs> SequenceDone;

    private List<Step> Steps;
    private System.IO.Ports.SerialPort comport = null;

    private Task SequenceTask;
    private CancellationTokenSource RequestStopSource;
    private CancellationToken RequestStopToken;


    private void Initialize()
    {
        comport = new System.IO.Ports.SerialPort("COM2", 115200, System.IO.Ports.Parity.None,8);
        comport.DataReceived += Comport_DataReceived;
    }

    public async void RunSequence()
    {
        if (comport == null)
        {
            Initialize();
        }
        if (!comport.IsOpen)
        {
            comport.Open();
        }

        RequestStopSource = new CancellationTokenSource();
        RequestStopToken = RequestStopSource.Token;

        SequenceTask = await Task.Factory.StartNew(async () => { await doSequence(); });

    }

    private Task doSequence()
    {
        //** Run Sequence stuff here

        //return null;
        return Task.CompletedTask;
    }
}

Answer 1

只需将doSequence标记为async(假设它使用await):

private async Task doSequence()

此外，最好在传递给 Task.Run 的委托(delegate)中返回此 Task:

SequenceTask = await Task.Run(() => doSequence());

I would like to create a task to run serial commands on.

这让我相信使用 async 和 Task 可能不是您场景的最佳解决方案。我建议您查看 TPL 数据流。