lparam and wparam in wpf app c#

Question

how to get LPARAM et WPARAM in WPF app C# to handle an usb connected device (a scaner panini vision x in my case)?

Mohamed Azarudeen Z · Answer

In a WPF app written in C#, you can handle USB-connected devices by using the Windows API. The WPARAM and LPARAM parameters are typically used in Windows message handling, but in this case, we'll be using them to handle USB device events. Here are the steps to get the WPARAM and LPARAM parameters in a WPF app to handle a USB-connected device: 1. Import the required namespaces: using System; using System.Windows; using System.Windows.Interop; using System.Runtime.InteropServices; 2. Define the Win32 API functions and constants required to handle USB events: [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)] public static extern IntPtr RegisterDeviceNotification(IntPtr hRecipient, IntPtr NotificationFilter, uint Flags); [DllImport("user32.dll", SetLastError = true)] public static extern bool UnregisterDeviceNotification(IntPtr Handle); private const int DBT_DEVICEARRIVAL = 0x8000; private const int DBT_DEVICEREMOVECOMPLETE = 0x8004; private const int DBT_DEVTYP_DEVICEINTERFACE = 0x0005; 3. Create a new `HwndSource` object to handle the USB device events: private HwndSource hwndSource; 4. Create a `Window_Loaded` event handler to register the device notification: private void Window_Loaded(object sender, RoutedEventArgs e) { hwndSource = HwndSource.FromHwnd(new WindowInteropHelper(this).Handle); hwndSource.AddHook(new HwndSourceHook(WndProc)); RegisterDeviceNotification(hwndSource.Handle, IntPtr.Zero, DBT_DEVTYP_DEVICEINTERFACE); } 5. Create a `WndProc` method to handle the USB device events: private IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled) { if (msg == WM_DEVICECHANGE) { if (wParam.ToInt32() == DBT_DEVICEARRIVAL) { // A new device has been connected DEV_BROADCAST_DEVICEINTERFACE devBroadcastDeviceInterface = (DEV_BROADCAST_DEVICEINTERFACE)Marshal.PtrToStructure(lParam, typeof(DEV_BROADCAST_DEVICEINTERFACE)); string deviceName = devBroadcastDeviceInterface.dbcc_name; // Handle the device event here } else if (wParam.ToInt32() == DBT_DEVICEREMOVECOMPLETE) { // A device has been disconnected DEV_BROADCAST_DEVICEINTERFACE devBroadcastDeviceInterface = (DEV_BROADCAST_DEVICEINTERFACE)Marshal.PtrToStructure(lParam, typeof(DEV_BROADCAST_DEVICEINTERFACE)); string deviceName = devBroadcastDeviceInterface.dbcc_name; // Handle the device event here } } return IntPtr.Zero; } In this example, we're handling the `DBT_DEVICEARRIVAL` and `DBT_DEVICEREMOVECOMPLETE` messages to detect when a device is connected or disconnected. The `lParam` parameter is used to extract the device name, which can be used to identify the device and handle the event accordingly. Note that you may need to modify the code to fit your specific USB device and use case.