using System.Runtime.InteropServices;
using System.Threading;

private const byte VK_SCROLL = 0x91;
private const byte VK_NUMLOCK = 0x90;
private const byte VK_CAPITAL = 0x14;
private const uint KEYEVENTF_KEYUP = 0x2;


[DllImport("user32.dll", EntryPoint = "keybd_event", SetLastError = true)]
static extern void keybd_event(byte bVk, byte bScan, uint dwFlags, uint dwExtraInfo);

[DllImport("user32.dll", EntryPoint = "GetKeyState", SetLastError = true)]
static extern short GetKeyState(uint nVirtKey);
//Scroll-------------------------------------------------------
public static void SetScrollLockKey(bool newState)
{
    bool scrollLockSet = GetKeyState(VK_SCROLL) != 0;
    if (scrollLockSet != newState)
    {
        keybd_event(VK_SCROLL, 0, 0, 0);
        keybd_event(VK_SCROLL, 0, KEYEVENTF_KEYUP, 0);
    }
}
public static bool GetScrollLockState()
{
    return GetKeyState(VK_SCROLL) != 0;
}
//NUM------------------------------------------------------- 
public static void SetNumLockKey(bool newState)
{
    bool scrollLockSet = GetKeyState(VK_NUMLOCK) != 0;
    if (scrollLockSet != newState)
    {
        keybd_event(VK_NUMLOCK, 0, 0, 0);
        keybd_event(VK_NUMLOCK, 0, KEYEVENTF_KEYUP, 0);
    }
}

public static bool GetNumLockState()
{
    return GetKeyState(VK_NUMLOCK) != 0;
}
//Caps-------------------------------------------------------
public static void SetCapsLockKey(bool newState)
{
    bool scrollLockSet = GetKeyState(VK_NUMLOCK) != 0;
    if (scrollLockSet != newState)
    {
        keybd_event(VK_CAPITAL, 0, 0, 0);
        keybd_event(VK_CAPITAL, 0, KEYEVENTF_KEYUP, 0);
    }
}

public static bool GetCapsLockState()
{
    return GetKeyState(VK_CAPITAL) != 0;
}

SetNumLockKey(true);
Thread.Sleep(100);
SetNumLockKey(false);
Thread.Sleep(100);
SetCapsLockKey(true);
Thread.Sleep(100);
SetCapsLockKey(false);
Thread.Sleep(100);
SetScrollLockKey(true);
Thread.Sleep(100); 
SetScrollLockKey(false);
Thread.Sleep(100); 

SetNumLockKey(true);

SetNumLockKey(false);

using System.Runtime.InteropServices;

[DllImport("user32.dll", SetLastError = false)]
static extern IntPtr GetDesktopWindow();

[DllImport("user32.dll", SetLastError = true)]
static extern IntPtr GetWindow(IntPtr hWnd, GetWindow_Cmd uCmd);

[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool EnableWindow(IntPtr hWnd, bool bEnable);

enum GetWindow_Cmd : uint
{
    GW_HWNDFIRST = 0,
    GW_HWNDLAST = 1,
    GW_HWNDNEXT = 2,
    GW_HWNDPREV = 3,
    GW_OWNER = 4,
    GW_CHILD = 5,
    GW_ENABLEDPOPUP = 6
}

private void button1_Click(object sender, EventArgs e)
{
    //получаем первое дочернее окно Рабочего стола
    IntPtr hwnd = GetWindow(GetDesktopWindow(), GetWindow_Cmd.GW_CHILD);
    if (hwnd != IntPtr.Zero)
    {
        //перебираем все окна в системе
        while (hwnd != IntPtr.Zero)
        {
            //проверка, что блокируем не свое окно
            if (hwnd != this.Handle)
            {
                //блокируем окно 
                //(вид окна, как будто его блокирует диалоговое окно)           
                EnableWindow(hwnd, false);
            }
            //получаем хендл следующего окна          
            hwnd = GetWindow(hwnd, GetWindow_Cmd.GW_HWNDNEXT);
        }
    }
}

[DllImport("user32.dll", SetLastError = true)]
private static extern void keybd_event( byte bVk, byte bScan, uint dwFlags, int dwExtraInfo );
 
private static void SendCtrlhotKey( char key ) {
  keybd_event(      0x11, 0,   0, 0);
  keybd_event( (byte)key, 0,   0, 0);
  keybd_event( (byte)key, 0, 0x2, 0);
  keybd_event(      0x11, 0, 0x2, 0);
}

SendCtrlhotKey( 'C' );

public Form1()
{
    InitializeComponent();
    timer1 = new Timer();
    this.timer1.Enabled = true;
    this.timer1.Interval = 777;
    this.timer1.Tick += new System.EventHandler(this.timer1_Tick);
    this.TopMost = true;
}

private void timer1_Tick(object sender, EventArgs e)
{
    label1.Text = GetKeyboardLayoutId();
}

[DllImport("user32.dll", CharSet = CharSet.Auto)]
private static extern IntPtr GetKeyboardLayout(int WindowsThreadProcessID);
[DllImport("user32.dll", CharSet = CharSet.Auto)]
private static extern int GetWindowThreadProcessId(IntPtr handleWindow, out int lpdwProcessID);
[DllImport("user32.dll", CharSet = CharSet.Auto)]
public static extern IntPtr GetForegroundWindow();

private static InputLanguageCollection _InstalledInputLanguages;
// Идентификатор активного потока
private static int _ProcessId;
// Текущий язык ввода
private static string _CurrentInputLanguage;


private static string GetKeyboardLayoutId()
{

    _InstalledInputLanguages = InputLanguage.InstalledInputLanguages;

    // Получаем хендл активного окна
    IntPtr hWnd = GetForegroundWindow();
    // Получаем номер потока активного окна
    int WinThreadProcId = GetWindowThreadProcessId(hWnd, out _ProcessId);

    // Получаем раскладку
    IntPtr KeybLayout = GetKeyboardLayout(WinThreadProcId);
    // Циклом перебираем все установленные языки для проверки идентификатора
    for (int i = 0; i < _InstalledInputLanguages.Count; i++)
    {
        if (KeybLayout == _InstalledInputLanguages[i].Handle)
        {
            _CurrentInputLanguage = _InstalledInputLanguages[i].Culture.ThreeLetterWindowsLanguageName.ToString();
        }
    }
    return _CurrentInputLanguage;

}