Question

I’m writing a DLL library that interfaces to a USB device using winusb in VB.NET.

Since it’s a DLL, I have no window, and it’s possible that users of my library will also not have a window (command line apps, for instance).

The examples I’ve seen that detect device attach and detach all use RegisterDeviceNotification which requires a window handle to receive the attach/detach messages at.

How do I receive these messages directly into a function without a window to get a handle from?

Answer 1

I recently found a solution that seems more elegant than RegisterDeviceNotification for an application without a GUI.

    void onEventArrived(object sender, EventArrivedEventArgs e)
    {
        ManagementBaseObject _o = e.NewEvent["TargetInstance"] as ManagementBaseObject;

        if (_o != null)
        {
            using (ManagementObject mo = new ManagementObject(_o["Dependent"].ToString()))
            {
                if (mo != null)
                {
                    try
                    {
                        if (mo.GetPropertyValue("DeviceID").ToString() != string.Empty)
                        {
                            //connected
                        }
                    }

                    catch (ManagementException ex)
                    {
                        //disconnected
                    }
                }
            }
        }
    }

Initialize this code by calling

        System.Management.WqlEventQuery _q = new WqlEventQuery("__InstanceOperationEvent", "TargetInstance ISA 'Win32_USBControllerDevice' ");
        _q.WithinInterval = TimeSpan.FromSeconds(1);
        ManagementEventWatcher _w = new ManagementEventWatcher(_q);
        _w.EventArrived += new EventArrivedEventHandler(onEventArrived);
        _w.Start();

Also make sure to add a reference to System.Management