Check for device change (add/remove) events
If you have a window in your application, you can use something like this:
using System;
using System.Runtime.InteropServices;
internal static class UsbNotification
{
public const int DbtDevicearrival = 0x8000; // system detected a new device
public const int DbtDeviceremovecomplete = 0x8004; // device is gone
public const int WmDevicechange = 0x0219; // device change event
private const int DbtDevtypDeviceinterface = 5;
private static readonly Guid GuidDevinterfaceUSBDevice = new Guid("A5DCBF10-6530-11D2-901F-00C04FB951ED"); // USB devices
private static IntPtr notificationHandle;
/// <summary>
/// Registers a window to receive notifications when USB devices are plugged or unplugged.
/// </summary>
/// <param name="windowHandle">Handle to the window receiving notifications.</param>
public static void RegisterUsbDeviceNotification(IntPtr windowHandle)
{
DevBroadcastDeviceinterface dbi = new DevBroadcastDeviceinterface
{
DeviceType = DbtDevtypDeviceinterface,
Reserved = 0,
ClassGuid = GuidDevinterfaceUSBDevice,
Name = 0
};
dbi.Size = Marshal.SizeOf(dbi);
IntPtr buffer = Marshal.AllocHGlobal(dbi.Size);
Marshal.StructureToPtr(dbi, buffer, true);
notificationHandle = RegisterDeviceNotification(windowHandle, buffer, 0);
}
/// <summary>
/// Unregisters the window for USB device notifications
/// </summary>
public static void UnregisterUsbDeviceNotification()
{
UnregisterDeviceNotification(notificationHandle);
}
[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
private static extern IntPtr RegisterDeviceNotification(IntPtr recipient, IntPtr notificationFilter, int flags);
[DllImport("user32.dll")]
private static extern bool UnregisterDeviceNotification(IntPtr handle);
[StructLayout(LayoutKind.Sequential)]
private struct DevBroadcastDeviceinterface
{
internal int Size;
internal int DeviceType;
internal int Reserved;
internal Guid ClassGuid;
internal short Name;
}
}
Here's how you use it from a WPF Window (Windows Forms is similar):
protected override void OnSourceInitialized(EventArgs e)
{
base.OnSourceInitialized(e);
// Adds the windows message processing hook and registers USB device add/removal notification.
HwndSource source = HwndSource.FromHwnd(new WindowInteropHelper(this).Handle);
if (source != null)
{
windowHandle = source.Handle;
source.AddHook(HwndHandler);
UsbNotification.RegisterUsbDeviceNotification(windowHandle);
}
}
/// <summary>
/// Method that receives window messages.
/// </summary>
private IntPtr HwndHandler(IntPtr hwnd, int msg, IntPtr wparam, IntPtr lparam, ref bool handled)
{
if (msg == UsbNotification.WmDevicechange)
{
switch ((int)wparam)
{
case UsbNotification.DbtDeviceremovecomplete:
Usb_DeviceRemoved(); // this is where you do your magic
break;
case UsbNotification.DbtDevicearrival:
Usb_DeviceAdded(); // this is where you do your magic
break;
}
}
handled = false;
return IntPtr.Zero;
}
Here's the use example for Windows Forms (even simpler):
public Form1()
{
InitializeComponent();
UsbNotification.RegisterUsbDeviceNotification(this.Handle);
}
protected override void WndProc(ref Message m)
{
base.WndProc(ref m);
if (m.Msg == UsbNotification.WmDevicechange)
{
switch ((int)m.WParam)
{
case UsbNotification.DbtDeviceremovecomplete:
Usb_DeviceRemoved(); // this is where you do your magic
break;
case UsbNotification.DbtDevicearrival:
Usb_DeviceAdded(); // this is where you do your magic
break;
}
}
}
Here is better version, because it can get port name. In case of DBT_DEVTYP_PORT device type, lParam points to DEV_BROADCAST_PORT, that contains DEV_BROADCAST_HDR and then name in Unicode of the device being removed or added ending with zeroes.
protected override void WndProc(ref Message m)
{
switch ((WndMessage) m.Msg)
{
case WndMessage.WM_DEVICECHANGE:
DEV_BROADCAST_HDR dbh;
switch ((WM_DEVICECHANGE) m.WParam)
{
case WM_DEVICECHANGE.DBT_DEVICEARRIVAL:
case WM_DEVICECHANGE.DBT_DEVICEREMOVECOMPLETE:
dbh = (DEV_BROADCAST_HDR) Marshal.PtrToStructure(m.LParam, typeof(DEV_BROADCAST_HDR));
if ((WM_DEVICECHANGE) dbh.dbch_devicetype == WM_DEVICECHANGE.DBT_DEVTYP_PORT)
{
var portNameBytes = new byte[dbh.dbch_size - (int) WM_DEVICECHANGE.SIZE_OF_DBH];
Marshal.Copy(m.LParam + (int) WM_DEVICECHANGE.SIZE_OF_DBH, portNameBytes, 0, portNameBytes.Length);
string portName = Encoding.Unicode.GetString(portNameBytes).TrimEnd('\0');
if (portName == Settings.Instance.PortName)
{
if ((WM_DEVICECHANGE) m.WParam == WM_DEVICECHANGE.DBT_DEVICEREMOVECOMPLETE)
{
if (!_port.IsOpen)
{
ClosePort();
}
}
else
{
BeginInvoke((Action) (() => OpenPort()));
}
}
}
break;
}
break;
}
base.WndProc(ref m);
}
public enum WndMessage
{
WM_DEVICECHANGE = 0x0219, // device change event
}
public enum WM_DEVICECHANGE
{
// full list: https://docs.microsoft.com/en-us/windows/win32/devio/wm-devicechange
DBT_DEVICEARRIVAL = 0x8000, // A device or piece of media has been inserted and is now available.
DBT_DEVICEREMOVECOMPLETE = 0x8004, // A device or piece of media has been removed.
DBT_DEVTYP_DEVICEINTERFACE = 0x00000005, // Class of devices. This structure is a DEV_BROADCAST_DEVICEINTERFACE structure.
DBT_DEVTYP_HANDLE = 0x00000006, // File system handle. This structure is a DEV_BROADCAST_HANDLE structure.
DBT_DEVTYP_OEM = 0x00000000, // OEM- or IHV-defined device type. This structure is a DEV_BROADCAST_OEM structure.
DBT_DEVTYP_PORT = 0x00000003, // Port device (serial or parallel). This structure is a DEV_BROADCAST_PORT structure.
DBT_DEVTYP_VOLUME = 0x00000002, // Logical volume. This structure is a DEV_BROADCAST_VOLUME structure.
SIZE_OF_DBH = 12, // sizeof(DEV_BROADCAST_HDR)
}
public struct DEV_BROADCAST_HDR
{
internal UInt32 dbch_size;
internal UInt32 dbch_devicetype;
internal UInt32 dbch_reserved;
};
I came to this post for a more specific case than the original question in that I want to be notified anytime a port is added or removed. For this situation the answer is much more simple and does not require calling RegisterDeviceNotification:
The DBT_DEVICEARRIVAL and DBT_DEVICEREMOVECOMPLETE events are automatically broadcast to all top-level windows for port devices. Therefore, it is not necessary to call RegisterDeviceNotification for ports....
https://docs.microsoft.com/en-us/windows/desktop/api/Winuser/nf-winuser-registerdevicenotificationa
So the solution becomes something like:
using System.Runtime.InteropServices;
//Put all of the following code inside your Form's partial class:
private struct DEV_BROADCAST_HDR {
internal UInt32 dbch_size;
internal UInt32 dbch_devicetype;
internal UInt32 dbch_reserved;
};
protected override void WndProc(ref Message m) {
base.WndProc(ref m); //This allows window default behavior of base class to be executed
if (m.Msg == 0x0219) { //WM_DEVICECHANGE = 0x0219
DEV_BROADCAST_HDR dbh;
switch ((int)m.WParam) {
case 0x8000: //DBT_DEVICEARRIVAL = 0x8000
dbh = (DEV_BROADCAST_HDR)Marshal.PtrToStructure(m.LParam, typeof(DEV_BROADCAST_HDR));
if (dbh.dbch_devicetype == 0x00000003) { //DBT_DEVTYP_PORT = 0x00000003
Console.WriteLine("Port added!");
//TODO
}
break;
case 0x8004: //DBT_DEVICEREMOVECOMPLETE = 0x8004
dbh = (DEV_BROADCAST_HDR)Marshal.PtrToStructure(m.LParam, typeof(DEV_BROADCAST_HDR));
if (dbh.dbch_devicetype == 0x00000003) { //DBT_DEVTYP_PORT = 0x00000003
Console.WriteLine("Port removed!");
//TODO
}
break;
}
}
}
The accepted answer is excellent, however it only works with USB devices.
To make it work with all devices (and optionally filter USB), use the following slightly modified class:
static class DeviceNotification {
//https://msdn.microsoft.com/en-us/library/aa363480(v=vs.85).aspx
public const int DbtDeviceArrival = 0x8000; // system detected a new device
public const int DbtDeviceRemoveComplete = 0x8004; // device is gone
public const int DbtDevNodesChanged = 0x0007; //A device has been added to or removed from the system.
public const int WmDevicechange = 0x0219; // device change event
private const int DbtDevtypDeviceinterface = 5;
//https://msdn.microsoft.com/en-us/library/aa363431(v=vs.85).aspx
private const int DEVICE_NOTIFY_ALL_INTERFACE_CLASSES = 4;
private static readonly Guid GuidDevinterfaceUSBDevice = new Guid("A5DCBF10-6530-11D2-901F-00C04FB951ED"); // USB devices
private static IntPtr notificationHandle;
/// <summary>
/// Registers a window to receive notifications when devices are plugged or unplugged.
/// </summary>
/// <param name="windowHandle">Handle to the window receiving notifications.</param>
/// <param name="usbOnly">true to filter to USB devices only, false to be notified for all devices.</param>
public static void RegisterDeviceNotification(IntPtr windowHandle, bool usbOnly = false) {
var dbi = new DevBroadcastDeviceinterface {
DeviceType = DbtDevtypDeviceinterface,
Reserved = 0,
ClassGuid = GuidDevinterfaceUSBDevice,
Name = 0
};
dbi.Size = Marshal.SizeOf(dbi);
IntPtr buffer = Marshal.AllocHGlobal(dbi.Size);
Marshal.StructureToPtr(dbi, buffer, true);
notificationHandle = RegisterDeviceNotification(windowHandle, buffer, usbOnly ? 0 : DEVICE_NOTIFY_ALL_INTERFACE_CLASSES);
}
/// <summary>
/// Unregisters the window for device notifications
/// </summary>
public static void UnregisterDeviceNotification() {
UnregisterDeviceNotification(notificationHandle);
}
[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
private static extern IntPtr RegisterDeviceNotification(IntPtr recipient, IntPtr notificationFilter, int flags);
[DllImport("user32.dll")]
private static extern bool UnregisterDeviceNotification(IntPtr handle);
[StructLayout(LayoutKind.Sequential)]
private struct DevBroadcastDeviceinterface {
internal int Size;
internal int DeviceType;
internal int Reserved;
internal Guid ClassGuid;
internal short Name;
}
}
The key change is the Flags parameter when calling RegisterDeviceNotification (see https://msdn.microsoft.com/en-us/library/aa363431(v=vs.85).aspx), which if set to 4 instead of 0 will ignore the ClassGuid parameter and register for all devices.