if you are using code behind then it is easy
using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;
public class CapsLockControl
{
[DllImport("user32.dll")]
static extern void keybd_event(byte bVk, byte bScan, uint dwFlags,UIntPtr dwExtraInfo);
const int KEYEVENTF_EXTENDEDKEY = 0x1;
const int KEYEVENTF_KEYUP = 0x2;
public static void Main()
{
if (Control.IsKeyLocked(Keys.CapsLock))
// Caps Lock key is ON.
else
// Caps Lock key is OFF
}
}