CODEWITHSUNDEEP
c#components
Allex
Allex

Reputation: 1

Using IMessageFilter not working under windows 7 64bit (C#, .net 2.0)

We are working on a USB device program. Following code snippet is my UsbComponent class. It works fine under windows XP or even windows 64 32bit. But under windows 7 64bit, PreFilterMessage never gets entered whenever I plugin/remove our USB device. Did I miss anything to make following code working under windows 7 64bit?

using System;
using System.ComponentModel;
using System.Collections.Generic;
using System.Diagnostics;
using System.Text;
using System.Windows.Forms;

public partial class UsbComponent : Component, IMessageFilter {
      private const int WM_DEVICECHANGE = 0x219;

      public UsbComponent() {
        InitializeComponent();
        Application.AddMessageFilter( this );
      }

      public UsbComponent( IContainer container ) {
        container.Add( this );
        InitializeComponent();
        Application.AddMessageFilter( this );
      }

      bool IMessageFilter.PreFilterMessage( ref Message m ) {
        if( m.Msg == WM_DEVICECHANGE ) {
          MessageBox.Show("device changed");
          return true;
        }
        return false;
      }
}

Upvotes: 0

Views: 2298

Answers (2)

OmarElsherif
OmarElsherif

Reputation: 31

An article in code project has stated that it's not possible to handle WM_DEVICECHANGE messages with IMessageFilter Interface, it suggests using of WndProc method which is available in System.Windows.Forms controls.

The following class is a private class within my class, it performs the work i need from the messages, it then rises an event to tell me about the result. I have to crate an object of it inside my class and handle its event.

This code detects the insertion or removal of HID class USB devices.

private class MyControl : Form, IMessageFilter
{
    Guid InterfaceClassGuid = new Guid(0x4d1e55b2, 0xf16f, 0x11cf, 0x88, 0xcb, 0x00, 0x11, 0x11, 0x00, 0x00, 0x30);

    //Constant definitions for certain WM_DEVICECHANGE messages
    private const uint WM_DEVICECHANGE = 0x0219;
    private const uint DBT_DEVICEARRIVAL = 0x8000;
    private const uint DBT_DEVICEREMOVEPENDING = 0x8003;
    private const uint DBT_DEVICEREMOVECOMPLETE = 0x8004;
    private const uint DBT_CONFIGCHANGED = 0x0018;

    //Other constant definitions
    private const uint DBT_DEVTYP_DEVICEINTERFACE = 0x05;
    private const uint DEVICE_NOTIFY_WINDOW_HANDLE = 0x00;

    private struct DEV_BROADCAST_DEVICEINTERFACE
    {
        internal uint dbcc_size;            //DWORD
        internal uint dbcc_devicetype;      //DWORD
        internal uint dbcc_reserved;        //DWORD
        internal Guid dbcc_classguid;       //GUID
        internal char[] dbcc_name;          //TCHAR array
    }

    //Need this function for receiving all of the WM_DEVICECHANGE messages.  See MSDN documentation for
    //description of what this function does/how to use it. Note: name is remapped "RegisterDeviceNotificationUM" to
    //avoid possible build error conflicts.
    [DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
    private static extern IntPtr RegisterDeviceNotification(
        IntPtr hRecipient,
        IntPtr NotificationFilter,
        uint Flags);

    public MyControl()
    {
        //Register for WM_DEVICECHANGE notifications.  This code uses these messages to detect plug and play connection/disconnection events for USB devices
        DEV_BROADCAST_DEVICEINTERFACE DeviceBroadcastHeader = new DEV_BROADCAST_DEVICEINTERFACE();
        DeviceBroadcastHeader.dbcc_devicetype = DBT_DEVTYP_DEVICEINTERFACE;
        DeviceBroadcastHeader.dbcc_size = (uint)Marshal.SizeOf(DeviceBroadcastHeader);
        DeviceBroadcastHeader.dbcc_reserved = 0;    //Reserved says not to use...
        DeviceBroadcastHeader.dbcc_classguid = InterfaceClassGuid;

        //Need to get the address of the DeviceBroadcastHeader to call RegisterDeviceNotification(), but
        //can't use "&DeviceBroadcastHeader".  Instead, using a roundabout means to get the address by 
        //making a duplicate copy using Marshal.StructureToPtr().
        IntPtr pDeviceBroadcastHeader = IntPtr.Zero;  //Make a pointer.
        pDeviceBroadcastHeader = Marshal.AllocHGlobal(Marshal.SizeOf(DeviceBroadcastHeader)); //allocate memory for a new DEV_BROADCAST_DEVICEINTERFACE structure, and return the address 
        Marshal.StructureToPtr(DeviceBroadcastHeader, pDeviceBroadcastHeader, false);  //Copies the DeviceBroadcastHeader structure into the memory already allocated at DeviceBroadcastHeaderWithPointer
        RegisterDeviceNotification(this.Handle, pDeviceBroadcastHeader, DEVICE_NOTIFY_WINDOW_HANDLE);
    }

    public event EventHandler DeviceConnected;

    protected override void WndProc(ref Message m)
    {
        if (m.Msg == WM_DEVICECHANGE)
        {
            if (((int)m.WParam == DBT_DEVICEARRIVAL) || ((int)m.WParam == DBT_DEVICEREMOVEPENDING) || ((int)m.WParam == DBT_DEVICEREMOVECOMPLETE) || ((int)m.WParam == DBT_CONFIGCHANGED))
            {
                //Rise the event, more processing is needed to check for a certain device.
                DeviceConnected(this, null);
            }
        }

        base.WndProc(ref m);
    }
}

Upvotes: 1

SwDevMan81
SwDevMan81

Reputation: 49988

It is the responsibility of the device driver to broadcast WM_DEVICECHANGE. Make sure you have the updated drivers for that device and verify that the device supports Windows 7

Upvotes: 0

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