C #. NET lock screen program (with blocking Task Manager)

Step 1: Set FormBorderStyle to none and WindowState to Maximized.

Occupies the entire screen.

Step 2: use hooks to monitor global Keyboard Events. This shields most system hotkeys. However, blocking ctrl + alt + del Task Manager is complicated. This special case will be discussed later.

Note when using global hooks: place the code in an independent class library (only dll can be injected into other processes ).

Using System;
Using System. Collections. Generic;
Using System. Text;
Using System. Runtime. InteropServices;
Using System. IO;
Using System. Reflection;

Namespace KeyboardHookDLL
{
Public class KeyboardHook
{
Public delegate int KeyboardProc (int nCode, IntPtr wParam, IntPtr lParam );

Static int hKeyboardHook = 0;
KeyboardProc KeyboardHookProcedure;

/// <Summary>
/// Hook function, which must reference space (using System. Reflection ;)
/// Set the thread hook to listen to the keyboard message to 2, and the global hook to listen to the keyboard message to 13
/// Set the mouse message to 7 for thread hook monitoring and the mouse message to 14 for global hook monitoring.
/// </Summary>

Public const int WH_KEYBOARD = 13;
Public const int WH_MOUSE_LL = 14;

Public struct KeyboardMSG
{
Public int vkCode;
Public int scanCode;
Public int flags;
Public int time;
Public int dwExtraInfo;

}
// Private FileStream MyFs;
// ASC codes of various key locations
Private const byte LLKHF_ALTDOWN = 0x20;
Private const byte VK_CAPITAL = 0x14;
Private const byte VK_ESCAPE = 0x1B;
Private const byte VK_F4 = 0x73;
Private const byte VK_LCONTROL = 0xA2;
Private const byte VK_NUMLOCK = 0x90;
Private const byte VK_RCONTROL = 0xA3;
Private const byte VK_SHIFT = 0x10;
Private const byte VK_TAB = 0x09;
// Public const int WH_KEYBOARD = 13;
Private const int WH_KEYBOARD_LL = 13;
Private const int WH_MOUSE = 7;
// Private const int WH_MOUSE_LL = 14;
Private const int WM_KEYDOWN = 0x100;
Private const int WM_KEYUP = 0x101;
Private const int WM_LBUTTONDBLCLK = 0x203;
Private const int WM_LBUTTONDOWN = 0x201;
Private const int WM_LBUTTONUP = 0x202;
Private const int WM_MBUTTONDBLCLK = 0x209;
Private const int WM_MBUTTONDOWN = 0x207;
Private const int WM_MBUTTONUP = 0x208;
Private const int WM_MOUSEMOVE = 0x200;
Private const int WM_MOUSEWHEEL = 0x020A;
Private const int WM_RBUTTONDBLCLK = 0x206;
Private const int WM_RBUTTONDOWN = 0x204;
Private const int WM_RBUTTONUP = 0x205;
Private const int WM_SYSKEYDOWN = 0x104;
Private const int WM_SYSKEYUP = 0x105;
// Private static int hKeyboardHook = 0;

/// <Summary>
/// The declaration method in vs2008 is slightly different in vs2010

/// </Summary>
/// <Returns> </returns>
[DllImport ("kernel32")]
Public static extern int GetCurrentThreadId ();

[DllImport ("user32.dll", CharSet = CharSet. Auto, CallingConvention =

CallingConvention. StdCall)]
Public static extern int SetWindowsHookEx (int idHook, KeyboardProc lpfn, IntPtr

HInstance, int threadId );

[DllImport ("user32.dll", CharSet = CharSet. Auto, CallingConvention =

CallingConvention. StdCall)]
Public static extern bool UnhookWindowsHookEx (int idHook );

[DllImport ("user32.dll", CharSet = CharSet. Auto, CallingConvention = CallingConvention. StdCall)]
Public static extern int CallNextHookEx (int idHook, int nCode, IntPtr wParam, IntPtr lParam );

[DllImport ("user32.dll", CharSet = CharSet. Auto, CallingConvention = CallingConvention. Winapi)]
Public static extern short GetKeyState (int keycode );

// Here you can define the key to intercept.
Private int KeyboardHookProc (int nCode, IntPtr wParam, IntPtr lParam)
{
KeyboardMSG m = (KeyboardMSG) Marshal. PtrToStructure (lParam, typeof (KeyboardMSG ));
If (
(Int) m. vkCode = 91) | (int) m. vkCode = 92) |
(M. vkCode = VK_TAB) & (m. flags & LLKHF_ALTDOWN )! = 0) |
(M. vkCode = VK_ESCAPE) & (m. flags & LLKHF_ALTDOWN )! = 0) |
(M. vkCode = VK_F4) & (m. flags & LLKHF_ALTDOWN )! = 0) |
(M. vkCode = VK_ESCAPE) & (GetKeyState (VK_LCONTROL) & 0x8000 )! = 0) |
(M. vkCode = VK_ESCAPE) & (GetKeyState (VK_RCONTROL) & 0x8000 )! = 0)
)
{
Return 1;
}
Return CallNextHookEx (hKeyboardHook, nCode, wParam, lParam );
& Nb