c# - 新 COM 端口可用事件

Question

我的 C# 应用程序使用 COM 端口。我遇到了一些大多数程序应该常见的困难。当端口名列表更改时，我需要获取一个事件。我有一个选择框，用户可以在其中从可用端口名称列表中进行选择。有没有人有这方面的代码片段？谢谢你。

Answer 1

它也可以在“ManagementEventWatcher”的帮助下完成：

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel.Composition;
using System.Linq;
using System.Text;
using System.Management;
using System.IO.Ports;
using System.Threading;
using System.Threading.Tasks;

namespace HmxFlashLoader
{
    /// <summary>
    /// Make sure you create this watcher in the UI thread if you are using the com port list in the UI
    /// </summary>
    [Export]
    [PartCreationPolicy(CreationPolicy.Shared)]
    public sealed class SerialPortWatcher : IDisposable
    {
        public SerialPortWatcher()
        {
            _taskScheduler = TaskScheduler.FromCurrentSynchronizationContext();
            ComPorts = new ObservableCollection<string>(SerialPort.GetPortNames().OrderBy(s => s));

            WqlEventQuery query = new WqlEventQuery("SELECT * FROM Win32_DeviceChangeEvent");

            _watcher = new ManagementEventWatcher(query);           
            _watcher.EventArrived += (sender, eventArgs) => CheckForNewPorts(eventArgs);
            _watcher.Start();       
        }

        private void CheckForNewPorts(EventArrivedEventArgs args)
        {
            // do it async so it is performed in the UI thread if this class has been created in the UI thread
            Task.Factory.StartNew(CheckForNewPortsAsync, CancellationToken.None, TaskCreationOptions.None, _taskScheduler);
        }

        private void CheckForNewPortsAsync()
        {
            IEnumerable<string> ports = SerialPort.GetPortNames().OrderBy(s => s);

            foreach (string comPort in ComPorts)
            {
                if (!ports.Contains(comPort))
                {
                    ComPorts.Remove(comPort);
                }
            }

            foreach (var port in ports)
            {           
                if (!ComPorts.Contains(port))
                {
                    AddPort(port);
                }
            }
        }

        private void AddPort(string port)
        {
            for (int j = 0; j < ComPorts.Count; j++)
            {
                if (port.CompareTo(ComPorts[j]) < 0)
                {
                    ComPorts.Insert(j, port);
                    break;
                }
            }

        }

        public ObservableCollection<string> ComPorts { get; private set; }

        #region IDisposable Members

        public void Dispose()
        {
            _watcher.Stop();    
        }

        #endregion

        private ManagementEventWatcher _watcher;
        private TaskScheduler _taskScheduler;
    }
}

Answer 2

创建一个简单的表单应用程序并将以下代码放入表单中：

protected override void WndProc(ref Message m)
{
    switch (m.Msg)
    {
        case 537: //WM_DEVICECHANGE
            var ports = SerialPort.GetPortNames().OrderBy(name => name);

            foreach (var portName in ports)
            {
                Debug.Print(portName);
            }
            break;
    }
    base.WndProc(ref m);
}

Answer 3

COM 端口更改是罕见事件，而不是常见事件。

最简单的方法是设置一个计时器，每 10-30 秒枚举一次 COM 端口列表，如果发生更改，更新列表。

更好的是，提供一个“刷新列表”按钮——列表基本上只有在用户插入 USB 串行适配器时才会改变。