连接或断开时检测USB到RS232转换器

您可以创建某种线程或任务来查询从方法System.IO.Ports.SerialPort.GetPortNames()返回的数组:当该数组更改或添加新元素时，这意味着新的串行端口已连接到系统。

当然，它将返回系统上的每个串行端口，但随后您可以使用代码片段选择其中哪些是USB-RS232转换器。

您可以使用MSSerial_PortName，请查找代码片段。

注意:这不是一个工作代码，你必须根据你的需求进行更改。

private void btn_tst2_Click(object sender, EventArgs e)
        {   
// connection to WMI rather than cimv2 namespace       
            ManagementObjectSearcher searcher = new ManagementObjectSearcher("root''WMI",
            "select * from MSSerial_PortName");
            foreach (ManagementObject queryObj in searcher.Get())
            {
               queryObj["Active"]; // status
               queryObj["InstanceName"];  
               queryObj["PortName"]; // port number
            }
        }

在经历了许多挫折之后，我终于找到了实现我所需要的东西的方法。我张贴的答案，以防它给一个指针，任何人在未来被困在同一地区。我在代码中包含了注释。我最后得到的是所有Com端口的列表，当一个离开或加入时，这个列表会刷新。文件dbt.h在您的PC上找到。

要使下面的代码工作，只需使用一个富文本框和两个按钮的解决方案。

    using System;
    using System.Collections.Generic;
    using System.ComponentModel;
    using System.Data;
    using System.Drawing;
    using System.Linq;
    using System.Text;
    using System.Threading.Tasks;
    using System.Windows.Forms;
    using System.Management;    //used to perform WMI queries
    using System.Threading;
    using System.Runtime.InteropServices; // needed for marshalling
    namespace MissionControl
    {
        public partial class Control : Form
        {
            public Control()
            {
                InitializeComponent();
            }
            // WndProc = Window Procedures: Every window has an associated     window procedure — a function that processes all messages sent 
        // or posted to all windows of the class. All aspects of a window's appearance and behavior depend on the window procedure's 
        // response to these messages. see https://msdn.microsoft.com/en-us/library/ms632593%28v=vs.85%29.aspx
        protected override void WndProc(ref Message m)
        {
            //you may find these definitions in dbt.h 
            const int WM_DEVICECHANGE = 0x0219; // in dbt.h, BroadcastSpecialMessage constants. 
            const int DBT_DEVICEARRIVAL = 0x8000;  // system detected a device arrived see dbt.h
            const int DBT_DEVICEREMOVECOMPLETE = 0x8004; //system detected a device removal see dbt.h
            const int DBT_DEVTYP_PORT = 0x00000003;  // serial, parallel in dbt.h
            switch (m.Msg)
            {
                case WM_DEVICECHANGE:
                    switch (m.WParam.ToInt32())
                    {
                        case DBT_DEVICEARRIVAL:
                            {
                                // Get the DBT_DEVTYP* as defined in dbt.h
                                // We are looking for DBT_DEVTYP_PORT value = 3 which is Serial port
                                int devTypeA = Marshal.ReadInt32(m.LParam, 4);
                                if (devTypeA == DBT_DEVTYP_PORT)
                                {
                                    rchtxbx_output.SelectedText = string.Empty;
                                    rchtxbx_output.SelectionFont = new Font(rchtxbx_output.SelectionFont, FontStyle.Bold);
                                    rchtxbx_output.SelectionColor = Color.Lime;
                                    rchtxbx_output.AppendText("'rSerial Port Connected'r'rList of Current Ports'r");
                                }
                                else
                                {
                                    // We should never get in here but just in case do somethign rather than fall over
                                    rchtxbx_output.SelectedText = string.Empty;
                                    rchtxbx_output.SelectionFont = new Font(rchtxbx_output.SelectionFont, FontStyle.Bold);
                                    rchtxbx_output.SelectionColor = Color.Red;
                                    rchtxbx_output.AppendText("Non-Serial Port Connected'r");
                                }

                                //To prevent cross threading we will start the function call in its own thread
                                // Create the thread object, passing in GetPortNum
                                //ThreadA is the arrival thread (just connected)
                                Thread ThreadA = new Thread(new ThreadStart(GetPortNum));
                                // Start the thread via a ThreadStart delegate
                                ThreadA.Start();
                            }
                            break;
                        case DBT_DEVICEREMOVECOMPLETE:
                            {
                                // Get the DBT_DEVTYP* as defined in dbt.h
                                // We are looking for DBT_DEVTYP_PORT value = 3 which is Serial port
                                int devTypeD = Marshal.ReadInt32(m.LParam, 4);
                                if (devTypeD == DBT_DEVTYP_PORT)
                                {
                                    rchtxbx_output.SelectedText = string.Empty;
                                    rchtxbx_output.SelectionFont = new Font(rchtxbx_output.SelectionFont, FontStyle.Bold);
                                    rchtxbx_output.SelectionColor = Color.Lime;
                                    rchtxbx_output.AppendText("'rSerial Port Disconnected'r'rList of Current Ports'r");
                                }
                                else
                                {
                                    // We should never get in here but just in case do something rather than fall over
                                    rchtxbx_output.SelectedText = string.Empty;
                                    rchtxbx_output.SelectionFont = new Font(rchtxbx_output.SelectionFont, FontStyle.Bold);
                                    rchtxbx_output.SelectionColor = Color.Red;
                                    rchtxbx_output.AppendText("Non-Serial Port Disconneted'r");
                                }
                                //To prevent cross threading we will start the function call in its own thread
                                // Create the thread object, passing in GetPortNum
                                //ThreadD is the departure thread (disconnected) 
                                Thread ThreadD = new Thread(new ThreadStart(GetPortNum));
                                // Start the thread via a ThreadStart delegate
                                ThreadD.Start();
                            }
                            break;
                    }
                    break;
            }
            //we detect the media arrival event 
            base.WndProc(ref m);
        }

        private void btn_close_Click(object sender, EventArgs e)
        {
            this.Close();
        }
        private void btn_clr_Click(object sender, EventArgs e)
        {
            rchtxbx_output.Clear();
        }
        private void GetPortNum()
        {
            //Windows Management Instrumentation (WMI) consists of a set of extensions to the Windows Driver Model that provides an 
            //operating system interface through which instrumented components provide information and notification. 
            // To work out the WMI to use, get the tool https://www.microsoft.com/en-us/download/details.aspx?id=8572
            //GUID (or UUID) is an acronym for 'Globally Unique Identifier' (or 'Universally Unique Identifier'). It is a 128-bit 
            //integer number used to identify resources. The term GUID is generally used by developers working with Microsoft 
            //technologies, while UUID is used everywhere else.
            // Get the list of ClassGUID from https://msdn.microsoft.com/en-us/library/windows/hardware/ff553426%28v=vs.85%29.aspx
            string comportnum = "";
            int textStart = 0;
            char[] textEnd = { ')' };

            ManagementObjectSearcher searcher = new ManagementObjectSearcher("root''CIMV2",
                    "SELECT * FROM Win32_PnPEntity WHERE ClassGuid='"{4d36e978-e325-11ce-bfc1-08002be10318}'"");
            foreach (ManagementObject queryObj in searcher.Get())
            {
                comportnum = queryObj["Name"].ToString(); // Get the name of the comm port
                //Format the string to extract the comport number only
                textStart = comportnum.IndexOf("(COM");
                comportnum = comportnum.Remove(0, textStart + 4).TrimEnd(textEnd);
                //To prevent cross threading use Invoke. We are writing to a control created in another thread.
                rchtxbx_output.Invoke(new EventHandler(delegate
                {
                    rchtxbx_output.SelectedText = string.Empty;
                    rchtxbx_output.SelectionFont = new Font(rchtxbx_output.SelectionFont, FontStyle.Bold);
                    rchtxbx_output.SelectionColor = Color.Lime; //set font colour
                    rchtxbx_output.AppendText("Comm Port = " + comportnum + "'r"); //add some text
                    rchtxbx_output.ScrollToCaret(); // move cursor to the end
                }));
            }
        }
    }
}