net 4.5中使用Async API的串行端口通信代码示例

我会使用TaskCompletionSource<>来包装SerialDataReceivedEvent，类似这样（未经测试）：

using System;
using System.IO.Ports;
using System.Threading;
using System.Threading.Tasks;
class PortDataReceived
{
    public static async Task ReadPort(SerialPort port, CancellationToken token)
    {
        while (true)
        {
            token.ThrowIfCancellationRequested();
            await TaskExt.FromEvent<SerialDataReceivedEventHandler, SerialDataReceivedEventArgs>(
                (complete, cancel, reject) => // get handler
                    (sender, args) => complete(args),
                handler => // subscribe
                    port.DataReceived += handler,
                handler => // unsubscribe
                    port.DataReceived -= handler,
                (complete, cancel, reject) => // start the operation
                    { if (port.BytesToRead != 0) complete(null); },
                token);
            Console.WriteLine("Received: " + port.ReadExisting());
        }
    }
    public static void Main()
    {
        SerialPort port = new SerialPort("COM1");
        port.BaudRate = 9600;
        port.Parity = Parity.None;
        port.StopBits = StopBits.One;
        port.DataBits = 8;
        port.Handshake = Handshake.None;
        port.Open();
        Console.WriteLine("Press Enter to stop...");
        Console.WriteLine();
        var cts = new CancellationTokenSource();
        var task = ReadPort(port, cts.Token);
        Console.ReadLine();
        cts.Cancel();
        try
        {
            task.Wait();
        }
        catch (AggregateException ex)
        {
            Console.WriteLine(ex.InnerException.Message);
        }
        port.Close();
    }
    // FromEvent<>, based on http://stackoverflow.com/a/22798789/1768303
    public static class TaskExt
    {
        public static async Task<TEventArgs> FromEvent<TEventHandler, TEventArgs>(
            Func<Action<TEventArgs>, Action, Action<Exception>, TEventHandler> getHandler,
            Action<TEventHandler> subscribe,
            Action<TEventHandler> unsubscribe,
            Action<Action<TEventArgs>, Action, Action<Exception>> initiate,
            CancellationToken token) where TEventHandler : class
        {
            var tcs = new TaskCompletionSource<TEventArgs>();
            Action<TEventArgs> complete = (args) => tcs.TrySetResult(args);
            Action cancel = () => tcs.TrySetCanceled();
            Action<Exception> reject = (ex) => tcs.TrySetException(ex);
            TEventHandler handler = getHandler(complete, cancel, reject);
            subscribe(handler);
            try
            {
                using (token.Register(() => tcs.TrySetCanceled()))
                {
                    initiate(complete, cancel, reject);
                    return await tcs.Task;
                }
            }
            finally
            {
                unsubscribe(handler);
            }
        }
    }
}

我在从UI线程关闭SerialPort时也遇到过类似的问题。下面的MSDN博客表明，这是由于UI线程和执行关闭操作的本机线程之间的死锁。http://blogs.msdn.com/b/bclteam/archive/2006/10/10/top-5-serialport-tips-_5b00_kim-hamilton_5d00_.aspx

将关闭放在一个单独的任务中为我修复了它。（该方法在我的项目中的Protocol容器类中实现，并在单击UI按钮、调用IDispose接口或关闭主窗口时调用。）

    public Task Close()
    {
        // Close the serial port in a new thread
        Task closeTask = new Task(() => 
        {
            try
            {
                serialPort.Close();
            }
            catch (IOException e)
            {
                // Port was not open
                throw e;
            }
        });
        closeTask.Start();
        return closeTask;
    }

然后在我的UI命令中。。。

        // The serial stream is stopped in a different thread so that the UI does
        // not get deadlocked with the stream waiting for events to complete.
        await serialStream.Close();

我认为您的问题很大程度上是让用户触发ReadDataAsync，并允许它在仍在进行读取时被触发（根据您的描述）。

正确的方法是在打开串行端口时启动读取，并在读取的完成处理程序中启动另一个读取（好吧，检查完成不是由端口关闭引起的）。

无论如何，从串行端口同时读取都是无用的，因为您无法控制传入数据移交给完整例程的顺序。