Enable & disable devices

Question

Hi all,

I am trying to disable then enable a usb device - like you can do in device manager. I have tried using devcon.exe and it works perfectly, apart from when the device has been or is being used. Under these circumstances it will tell me that the device will be disabled after restarting the system. I don’t want the system to be restarted!! Subsequently my question is: is it possible to force the disabling of a usb device or fake the reboot (maybe by restarting a number of services).

Thanks for your help John

Answer 1

Here is some code that can be modified to accommodate your needs.

using System;
using System.Collections.Generic;
using System.Text;
using System.Management;

namespace DeviceMonitor.Event
{
 /// <summary>Media watcher delegate.</summary>
 /// <param name="sender"></param>
 /// <param name="driveStatus"></param>
 public delegate void MediaWatcherEventHandler( object sender, DeviceMonitor.Event.MediaEvent.DriveStatus driveStatus );
 /// <summary>Class to monitor devices.</summary>
 public class MediaEvent
 {
  #region Variables

  /*------------------------------------------------------------------------*/
  private string m_logicalDrive;
  private ManagementEventWatcher m_managementEventWatcher = null;
  /*------------------------------------------------------------------------*/
  #endregion

  #region Events
  /*------------------------------------------------------------------------*/
  public event MediaWatcherEventHandler MediaWatcher;
  /*------------------------------------------------------------------------*/
  #endregion


  #region Enums
  /*------------------------------------------------------------------------*/
  /// <summary>The drive types.</summary>
  public enum DriveType
  {
   Unknown = 0,
   NoRootDirectory = 1,
   RemoveableDisk  = 2,
   LocalDisk       = 3,
   NetworkDrive    = 4,
   CompactDisk     = 5,
   RamDisk         = 6
  }

  /// <summary>The drive status.</summary>
  public enum DriveStatus
  {
   Unknown  = -1,
   Ejected  = 0,
   Inserted = 1,
  }
  /*-----------------------------------------------------------------------*/
  #endregion


  #region Monitoring
  /*-----------------------------------------------------------------------*/
  /// <summary>Starts the monitoring of device.</summary>
  /// <param name="path"></param>
  /// <param name="mediaEvent"></param>
  public void Monitor( string path, MediaEvent mediaEvent ) {
   if( null == mediaEvent ) {
    throw new ArgumentException( "Media event cannot be null!" );
   }

   //In case same class was called make sure only one instance is running
   /////////////////////////////////////////////////////////////
   this.Exit();

   //Keep logica drive to check
   /////////////////////////////////////////////////////////////
   this.m_logicalDrive = this.GetLogicalDrive( path );

   WqlEventQuery wql;
   ManagementOperationObserver observer = new
       ManagementOperationObserver();

   //Bind to local machine
   /////////////////////////////////////////////////////////////
   ConnectionOptions opt = new ConnectionOptions();

   //Sets required privilege
   /////////////////////////////////////////////////////////////
   opt.EnablePrivileges = true;
   ManagementScope scope = new ManagementScope( "root\\CIMV2", opt );

   try {
    wql = new WqlEventQuery();
    wql.EventClassName = "__InstanceModificationEvent";
    wql.WithinInterval = new TimeSpan( 0, 0, 1 );

    wql.Condition = String.Format( @"TargetInstance ISA 'Win32_LogicalDisk' and TargetInstance.DeviceId = '{0}'", this.m_logicalDrive );
    this.m_managementEventWatcher = new ManagementEventWatcher( scope, wql );

    //Register async. event handler
    /////////////////////////////////////////////////////////////
    this.m_managementEventWatcher.EventArrived += new EventArrivedEventHandler( mediaEvent.MediaEventArrived );
    this.m_managementEventWatcher.Start();
   } catch( Exception e ) {
    this.Exit();
    throw new Exception( "Media Check: "  + e.Message );
   }
  }

  /// <summary>Stops the monitoring of device.</summary>
  public void Exit( ) {
   //In case same class was called make sure only one instance is running
   /////////////////////////////////////////////////////////////
   if( null != this.m_managementEventWatcher ) {
    try {
     this.m_managementEventWatcher.Stop();
     this.m_managementEventWatcher = null;
    } catch {
    }
   }
  }
  /*-----------------------------------------------------------------------*/
  #endregion


  #region Helpers
  /*-----------------------------------------------------------------------*/

  private DriveStatus m_driveStatus = DriveStatus.Unknown;
  /// <summary>Triggers the event when change on device occured.</summary>
  /// <param name="sender"></param>
  /// <param name="e"></param>
  private void MediaEventArrived( object sender, EventArrivedEventArgs e ) {
   // Get the Event object and display it
   PropertyData pd = e.NewEvent.Properties["TargetInstance"];
   DriveStatus driveStatus = this.m_driveStatus;
   if( pd != null ) {
    ManagementBaseObject mbo = pd.Value as ManagementBaseObject;
    System.IO.DriveInfo info = new System.IO.DriveInfo( (string)mbo.Properties["DeviceID"].Value );
    driveStatus = info.IsReady ? DriveStatus.Inserted : DriveStatus.Ejected;
   }

   if( driveStatus != this.m_driveStatus ){
    this.m_driveStatus = driveStatus;
    if( null != MediaWatcher ) {
     MediaWatcher( sender, driveStatus );
    }
   }
  }


  /// <summary>Gets the logical drive of a given path.</summary>
  /// <param name="path"></param>
  /// <returns></returns>
  private string GetLogicalDrive( string path ) {
   System.IO.DirectoryInfo dirInfo = new System.IO.DirectoryInfo( path );
   string root = dirInfo.Root.FullName;
   string logicalDrive = root.Remove( root.IndexOf( System.IO.Path.DirectorySeparatorChar ) );
   return logicalDrive;
  }
  /*-----------------------------------------------------------------------*/
  #endregion
 }
}

I found this on MSDN at:

http://social.msdn.microsoft.com/forums/en-US/csharpgeneral/thread/09912cee-4d2d-4efd-82a0-da20024b868b/

Answer 2

The function used by device manager and devcon.exe is SetupDiChangeState.

But it seems like your problem is related to the device being in-use more than the details of disabling it. There are tools like oh.exe (List Open Handles) that could help find out what applications need to be closed, they are implemented by passing undocumented flags to NtQueryInformationProcess.