Thoughts on Software Engineering

Enumerate All COM Ports and Find Their Name and Description in C#

I needed to enumerate all COM ports in C# and get their name (e.g. COM1, COM2, …) and their description shown in the Windows Device Manager (e.g. “Communications Port”, “RT USB MRTD Reader”). You could find lots of unmanaged code for doing this but I think this C# code could be helpful to people who perform communication through the serial interface in .NET:

using System;
using System.Text;
using ComTypes = System.Runtime.InteropServices.ComTypes;
using System.Runtime.InteropServices;
using System.Collections.Generic;

public class Win32DeviceMgmt
    private const UInt32 DIGCF_PRESENT = 0x00000002;
    private const UInt32 DIGCF_DEVICEINTERFACE = 0x00000010;
    private const UInt32 SPDRP_DEVICEDESC = 0x00000000;
    private const UInt32 DICS_FLAG_GLOBAL = 0x00000001;
    private const UInt32 DIREG_DEV = 0x00000001;
    private const UInt32 KEY_QUERY_VALUE = 0x0001;
    private const string GUID_DEVINTERFACE_COMPORT = "86E0D1E0-8089-11D0-9CE4-08003E301F73";

    private struct SP_DEVINFO_DATA
        public Int32  cbSize;
        public Guid   ClassGuid;
        public Int32  DevInst;
        public UIntPtr Reserved;

    private static extern Int32 SetupDiDestroyDeviceInfoList(IntPtr DeviceInfoSet);

    private static extern bool SetupDiEnumDeviceInfo(IntPtr DeviceInfoSet, Int32 MemberIndex, ref  SP_DEVINFO_DATA DeviceInterfaceData);

    [DllImport("setupapi.dll", CharSet = CharSet.Auto, SetLastError = true)]
    private static extern bool SetupDiGetDeviceRegistryProperty(IntPtr deviceInfoSet, ref SP_DEVINFO_DATA deviceInfoData,
        uint property, out UInt32 propertyRegDataType, StringBuilder propertyBuffer, uint propertyBufferSize, out UInt32 requiredSize);

    [DllImport("setupapi.dll", SetLastError = true)]
    private static extern IntPtr SetupDiGetClassDevs(ref Guid gClass, UInt32 iEnumerator, IntPtr hParent, UInt32 nFlags);

    [DllImport("Setupapi", CharSet = CharSet.Auto, SetLastError = true)]
    private static extern IntPtr SetupDiOpenDevRegKey(IntPtr hDeviceInfoSet, ref SP_DEVINFO_DATA deviceInfoData, uint scope,
        uint hwProfile, uint parameterRegistryValueKind, uint samDesired);

    [DllImport("advapi32.dll", CharSet = CharSet.Unicode, EntryPoint = "RegQueryValueExW", SetLastError = true)]
    private static extern int RegQueryValueEx(IntPtr hKey, string lpValueName, int lpReserved, out uint lpType,
        StringBuilder lpData, ref uint lpcbData);

    [DllImport("advapi32.dll", CharSet = CharSet.Ansi, SetLastError = true, ExactSpelling = true)]
    private static extern int RegCloseKey(IntPtr hKey);

    private static extern Int32 GetLastError();

    public struct DeviceInfo
        public string name;
        public string decsription;

    public static List<DeviceInfo> GetAllCOMPorts()
        Guid guidComPorts = new Guid(GUID_DEVINTERFACE_COMPORT);
        IntPtr hDeviceInfoSet = SetupDiGetClassDevs(
            ref guidComPorts, 0, IntPtr.Zero, DIGCF_PRESENT | DIGCF_DEVICEINTERFACE);
        if (hDeviceInfoSet == IntPtr.Zero)
            throw new Exception("Failed to get device information set for the COM ports");

        try {
            List<DeviceInfo> devices = new List<DeviceInfo>();
            Int32 iMemberIndex = 0;
            while (true)
                SP_DEVINFO_DATA deviceInfoData = new SP_DEVINFO_DATA();
                deviceInfoData.cbSize = Marshal.SizeOf(typeof(SP_DEVINFO_DATA));
                bool success = SetupDiEnumDeviceInfo(hDeviceInfoSet, iMemberIndex, ref deviceInfoData);
                if (!success)
                    // No more devices in the device information set

                DeviceInfo deviceInfo = new DeviceInfo();
       = GetDeviceName(hDeviceInfoSet, deviceInfoData);
                deviceInfo.decsription = GetDeviceDescription(hDeviceInfoSet, deviceInfoData);

            return devices;
        finally {

    private static string GetDeviceName(IntPtr pDevInfoSet, SP_DEVINFO_DATA deviceInfoData)
        IntPtr hDeviceRegistryKey = SetupDiOpenDevRegKey(pDevInfoSet, ref deviceInfoData,
        if (hDeviceRegistryKey == IntPtr.Zero)
            throw new Exception("Failed to open a registry key for device-specific configuration information");

        StringBuilder deviceNameBuf = new StringBuilder(256);
            uint lpRegKeyType;
            uint length = (uint)deviceNameBuf.Capacity;
            int result = RegQueryValueEx(hDeviceRegistryKey, "PortName", 0, out lpRegKeyType, deviceNameBuf, ref length);
            if (result != 0)
                throw new Exception("Can not read registry value PortName for device " + deviceInfoData.ClassGuid);

        string deviceName = deviceNameBuf.ToString();
        return deviceName;

    private static string GetDeviceDescription(IntPtr hDeviceInfoSet, SP_DEVINFO_DATA deviceInfoData)
        StringBuilder descriptionBuf = new StringBuilder(256);
        uint propRegDataType;
        uint length = (uint)descriptionBuf.Capacity;
        bool success = SetupDiGetDeviceRegistryProperty(hDeviceInfoSet, ref deviceInfoData, SPDRP_DEVICEDESC,
            out propRegDataType, descriptionBuf, length, out length);
        if (!success)
            throw new Exception("Can not read registry value PortName for device " + deviceInfoData.ClassGuid);
        string deviceDescription = descriptionBuf.ToString();
        return deviceDescription;

Previews (7,037), Views (3,115), Comments (10)

10 Responses to “Enumerate All COM Ports and Find Their Name and Description in C#”

  1. Jimmy Abu Al Denien says:

    What this means?
    List< and >

    Thx for the Code.


  2. Karel says:

    Great code, helped me a lot!!!

  3. Dan says:

    Perfect… I’d like to say simple, but after hours of trying to do this on my own I know that you only made it look simple. Thank You.

  4. Segun Ilori says:

    Please Note: The < and > mean greater than and less than. replace with “”

  5. Segun Ilori says:

    Please Note: The & lt ; and & gt ; mean greater than and less than. replace with “ <” and “>”

  6. nakov says:

    I know about “< " and ">“. This is a problem in the WordPress content editor.

  7. Works like a charm. Thank you.

  8. Argo says:

    Works like a charm. Best code i’ve found. Good work, my vote of 5/5.

  9. Mischo says:

    Thanks for amazing piece of code. Most of online published codes uses Windows queries, whose take about 1 second to execute. This codes runs in few milliseconds!

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