Hi!
I need to prevent Task-Switching in my App, so I tried to implement a
low level keyboard hook in a extra class. But it seems that the
Parameters are not passed correctly to my Hook function. Similar
Examples in VB .NET work correctly.
Heres the Source Code:
using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;
using System.Diagnostics;
public class LowLevelKeyboardHook :IDisposable
{
[DllImport("user32.dll")]
private static extern int SetWindowsHookExA(int IDHook, IntPtr lpfn,
int hMod,
int dwThreadID);
[DllImport("user32.dll")]
private static extern int UnhookWindowsHookEx(int hHook);
[DllImport("user32.dll")]
private static extern int CallNextHookEx(int hHook, int nCode, int
wParam, ref KBDLLHOOKSTRUCT lParam);
private delegate int LowLevelKeyboardProc(int nCode, int wParam,
KBDLLHOOKSTRUCT lParam);
public struct KBDLLHOOKSTRUCT
{
public int vkCode;
public int scanCode;
public int flags;
public int time;
public int dwExtraInfo;
}
private const int WH_KEYBOARD_LL = 13;
private int intLLKey;
public LowLevelKeyboardHook()
{
intLLKey = SetWindowsHookExA(WH_KEYBOARD_LL, new
LowLevelKeyboardProc(WindowKeyHook).Method.MethodH andle.GetFunctionPointer(),
System.Runtime.InteropServices.Marshal.GetHINSTANC E(System.Reflection.Assembly.GetExecutingAssembly( ).GetModules()[0]).ToInt32(),
0);
}
public int WindowKeyHook(int nCode, int wParam, KBDLLHOOKSTRUCT
lParam)
{
bool killKey = false;
if(killKey)
{
return 1;
}
else
{
return 0;
}
}
public void Dispose()
{
UnhookWindowsHookEx(intLLKey);
}
}
[b:2c1b8f9cf8]and the VB-Code, which worked[/b:2c1b8f9cf8]
Public Class frmMain
Inherits System.Windows.Forms.Form
Declare Function SetWindowsHookEx Lib "user32" Alias
"SetWindowsHookExA" (ByVal idHook As Integer, ByVal lpfn As
LowLevelKeyboardProcDelegate, ByVal hMod As Integer, ByVal dwThreadId
As Integer) As Integer
Declare Function UnhookWindowsHookEx Lib "user32" Alias
"UnhookWindowsHookEx" (ByVal hHook As Integer) As Integer
Delegate Function LowLevelKeyboardProcDelegate(ByVal nCode As
Integer, ByVal wParam As Integer, ByRef lParam As KBDLLHOOKSTRUCT) As
Integer
Declare Function CallNextHookEx Lib "user32" Alias
"CallNextHookEx" (ByVal hHook As Integer, ByVal nCode As Integer,
ByVal wParam As Integer, ByRef lParam As KBDLLHOOKSTRUCT) As Integer
Const WH_KEYBOARD_LL = 13
Structure KBDLLHOOKSTRUCT
Dim vkCode As Integer
Dim scanCode As Integer
Dim flags As Integer
Dim time As Integer
Dim dwExtraInfo As Integer
End Structure
Dim intLLKey As Integer
#Region " Windows Form Designer generated code "
Public Sub New()
MyBase.New()
'This call is required by the Windows Form Designer.
InitializeComponent()
'Add any initialization after the InitializeComponent() call
End Sub
'Form overrides dispose to clean up the component list.
Protected Overloads Overrides Sub Dispose(ByVal disposing As
Boolean)
If disposing Then
If Not (components Is Nothing) Then
components.Dispose()
End If
End If
MyBase.Dispose(disposing)
End Sub
'Required by the Windows Form Designer
Private components As System.ComponentModel.IContainer
'NOTE: The following procedure is required by the Windows Form
Designer
'It can be modified using the Windows Form Designer.
'Do not modify it using the code editor.
<System.Diagnostics.DebuggerStepThrough()> Private Sub
InitializeComponent()
Me.lblInfo = New System.Windows.Forms.Label()
Me.SuspendLayout()
'
'lblInfo
'
Me.lblInfo.Location = New System.Drawing.Point(16, 16)
Me.lblInfo.Name = "lblInfo"
Me.lblInfo.Size = New System.Drawing.Size(216, 88)
Me.lblInfo.TabIndex = 0
Me.lblInfo.Text = "Alt-Tab, Alt-Esc, Ctrl-Esc, and the Windows
key are disabled. Ctrl-Alt-Del and Al" & _
"t-F4 are still enabled. Close the application to reset the
keyboard. While this " & _
"program is running, the low-level keyboard effect is
global."
'
'frmMain
'
Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)
Me.ClientSize = New System.Drawing.Size(248, 118)
Me.Controls.AddRange(New System.Windows.Forms.Control()
{Me.lblInfo})
Me.FormBorderStyle =
System.Windows.Forms.FormBorderStyle.FixedDialog
Me.MaximizeBox = False
Me.MinimizeBox = False
Me.Name = "frmMain"
Me.StartPosition =
System.Windows.Forms.FormStartPosition.CenterScree n
Me.Text = "LowLevel Keyboard Hook"
Me.ResumeLayout(False)
End Sub
#End Region
Private Sub frmMain_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
intLLKey = SetWindowsHookEx(WH_KEYBOARD_LL, AddressOf
LowLevelKeyboardProc,
System.Runtime.InteropServices.Marshal.GetHINSTANC E(System.Reflection.Assembly.GetExecutingAssembly. GetModules()(0)).ToInt32(),
0)
End Sub
Private Sub frmMain_Closing(ByVal sender As Object, ByVal e As
System.ComponentModel.CancelEventArgs) Handles MyBase.Closing
UnhookWindowsHookEx(intLLKey)
End Sub
Private Function LowLevelKeyboardProc(ByVal nCode As Integer,
ByVal wParam As Integer, ByRef lParam As KBDLLHOOKSTRUCT) As Integer
Dim blnEat As Boolean = False
Debug.WriteLine(nCode.ToString())
Select Case wParam
Case 256, 257, 260, 261
'Alt+Tab, Alt+Esc, Ctrl+Esc, Windows Key
blnEat = ((lParam.vkCode = 9) AndAlso (lParam.flags =
32)) Or _
((lParam.vkCode = 27) AndAlso (lParam.flags = 32))
Or _
((lParam.vkCode = 27) AndAlso (lParam.flags = 0))
Or _
((lParam.vkCode = 91) AndAlso (lParam.flags = 1))
Or _
((lParam.vkCode = 92) AndAlso (lParam.flags = 1))
End Select
If blnEat = True Then
Return 1
Else
Return CallNextHookEx(0, nCode, wParam, lParam)
End If
End Function
Friend WithEvents lblInfo As System.Windows.Forms.Label
End Class
hopefully somebody can help me!
thanks daFritz
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