C# Signature:
[DllImport("advapi32.dll", SetLastError=true)]
static extern int RegNotifyChangeKeyValue(IntPtr hKey, bool watchSubtree,
int dwNotifyFilter, IntPtr hEvent, bool fAsynchronous);
VB Signature:
Declare Function RegNotifyChangeKeyValue Lib "advapi32.dll" (hKey As IntPtr, _
watchSubtree As Boolean, dwNotifyFilter As Integer, hEvent As IntPtr,
fAsynchronous As Boolean) As Integer
Notes:
Starting with the .NET Framework 2.0, the IntPtr parameters could be defined as SafeHandle instead.
Tips & Tricks:
Please add some!
Sample Code:
using System;
using System.ComponentModel;
using System.Diagnostics;
using System.Reflection;
using System.Runtime.InteropServices;
using System.Threading;
using Microsoft.Win32;
namespace BBooth
{
#region Delegates
public delegate void RegistryChangeHandler(object sender, RegistryChangeEventArgs e);
#endregion
public class RegistryChangeMonitor : IDisposable
{
#region Fields
private string _registryPath;
private REG_NOTIFY_CHANGE _filter;
private Thread _monitorThread;
private RegistryKey _monitorKey;
#endregion
#region Imports
[DllImport("Advapi32.dll")]
private static extern int RegNotifyChangeKeyValue(
IntPtr hKey,
bool watchSubtree,
REG_NOTIFY_CHANGE notifyFilter,
IntPtr hEvent,
bool asynchronous
);
#endregion
#region Enumerations
[Flags]
public enum REG_NOTIFY_CHANGE : uint
{
NAME = 0x1,
ATTRIBUTES = 0x2,
LAST_SET = 0x4,
SECURITY = 0x8
}
#endregion
#region Constructors
public RegistryChangeMonitor(string registryPath) : this(registryPath, REG_NOTIFY_CHANGE.LAST_SET) { ; }
public RegistryChangeMonitor(string registryPath, REG_NOTIFY_CHANGE filter)
{
this._registryPath = registryPath.ToUpper();
this._filter = filter;
}
~RegistryChangeMonitor()
{
this.Dispose(false);
}
#endregion
#region Methods
private void Dispose(bool disposing)
{
if (disposing)
GC.SuppressFinalize(this);
this.Stop();
}
public void Dispose()
{
this.Dispose(true);
}
public void Start()
{
lock (this)
{
if (this._monitorThread == null)
{
ThreadStart ts = new ThreadStart(this.MonitorThread);
this._monitorThread = new Thread(ts);
this._monitorThread.IsBackground = true;
}
if (!this._monitorThread.IsAlive)
{
this._monitorThread.Start();
}
}
}
public void Stop()
{
lock (this)
{
this.Changed = null;
this.Error = null;
if (this._monitorThread != null)
{
this._monitorThread = null;
}
// The "Close()" will trigger RegNotifyChangeKeyValue if it is still listening
if (this._monitorKey != null)
{
this._monitorKey.Close();
this._monitorKey = null;
}
}
}
private void MonitorThread()
{
try
{
IntPtr ptr = IntPtr.Zero;
lock (this)
{
if (this._registryPath.StartsWith("HKEY_CLASSES_ROOT"))
this._monitorKey = Registry.ClassesRoot.OpenSubKey(this._registryPath.Substring(18));
else if (this._registryPath.StartsWith("HKCR"))
this._monitorKey = Registry.ClassesRoot.OpenSubKey(this._registryPath.Substring(5));
else if (this._registryPath.StartsWith("HKEY_CURRENT_USER"))
this._monitorKey = Registry.CurrentUser.OpenSubKey(this._registryPath.Substring(18));
else if (this._registryPath.StartsWith("HKCU"))
this._monitorKey = Registry.CurrentUser.OpenSubKey(this._registryPath.Substring(5));
else if (this._registryPath.StartsWith("HKEY_LOCAL_MACHINE"))
this._monitorKey = Registry.LocalMachine.OpenSubKey(this._registryPath.Substring(19));
else if (this._registryPath.StartsWith("HKLM"))
this._monitorKey = Registry.LocalMachine.OpenSubKey(this._registryPath.Substring(5));
else if (this._registryPath.StartsWith("HKEY_USERS"))
this._monitorKey = Registry.Users.OpenSubKey(this._registryPath.Substring(11));
else if (this._registryPath.StartsWith("HKU"))
this._monitorKey = Registry.Users.OpenSubKey(this._registryPath.Substring(4));
else if (this._registryPath.StartsWith("HKEY_CURRENT_CONFIG"))
this._monitorKey = Registry.CurrentConfig.OpenSubKey(this._registryPath.Substring(20));
else if (this._registryPath.StartsWith("HKCC"))
this._monitorKey = Registry.CurrentConfig.OpenSubKey(this._registryPath.Substring(5));
// Fetch the native handle
if (this._monitorKey != null)
{
object hkey = typeof(RegistryKey).InvokeMember(
"hkey",
BindingFlags.GetField | BindingFlags.Instance | BindingFlags.NonPublic,
null,
this._monitorKey,
null
);
ptr = (IntPtr)typeof(SafeHandle).InvokeMember(
"handle",
BindingFlags.GetField | BindingFlags.Instance | BindingFlags.NonPublic,
null,
hkey,
null);
}
}
if (ptr != IntPtr.Zero)
{
while (true)
{
// If this._monitorThread is null that probably means Dispose is being called. Don't monitor anymore.
if ((this._monitorThread == null) || (this._monitorKey == null))
break;
// RegNotifyChangeKeyValue blocks until a change occurs.
int result = RegNotifyChangeKeyValue(ptr, true, this._filter, IntPtr.Zero, false);
if ((this._monitorThread == null) || (this._monitorKey == null))
break;
if (result == 0)
{
if (this.Changed != null)
{
RegistryChangeEventArgs e = new RegistryChangeEventArgs(this);
this.Changed(this, e);
if (e.Stop) break;
}
}
else
{
if (this.Error != null)
{
Win32Exception ex = new Win32Exception();
// Unless the exception is thrown, nobody is nice enough to set a good stacktrace for us. Set it ourselves.
typeof(Exception).InvokeMember(
"_stackTrace",
BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.SetField,
null,
ex,
new object[] { new StackTrace(true) }
);
RegistryChangeEventArgs e = new RegistryChangeEventArgs(this);
e.Exception = ex;
this.Error(this, e);
}
break;
}
}
}
}
catch (Exception ex)
{
if (this.Error != null)
{
RegistryChangeEventArgs e = new RegistryChangeEventArgs(this);
e.Exception = ex;
this.Error(this, e);
}
}
finally
{
this.Stop();
}
}
#endregion
#region Events
public event RegistryChangeHandler Changed;
public event RegistryChangeHandler Error;
#endregion
#region Properties
public bool Monitoring
{
get
{
if (this._monitorThread != null)
return this._monitorThread.IsAlive;
return false;
}
}
#endregion
}
}
using System;
namespace BBooth
{
public class RegistryChangeEventArgs : EventArgs
{
#region Fields
private bool _stop;
private Exception _exception;
private RegistryChangeMonitor _monitor;
#endregion
#region Constructor
public RegistryChangeEventArgs(RegistryChangeMonitor monitor)
{
this._monitor = monitor;
}
#endregion
#region Properties
public RegistryChangeMonitor Monitor
{
get { return this._monitor; }
}
public Exception Exception
{
get { return this._exception; }
set { this._exception = value; }
}
public bool Stop
{
get { return this._stop; }
set { this._stop = value; }
}
#endregion
}
}
Alternative Managed API:
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