I've been searching for a while and there are mostly results in C++ or other languages, and not C#. Things I've seen:
keybd_event() // A c++ method that theoretically can be included with a DLL import, but hasn't worked in testing
System.Windows.Forms.SendKeys.Send("{NUMLOCK}"}; // Forms namespace doesn't exist in Windows
Currently, I have code that executes every second or so to watch the state of numlock and update a graphic in my form accordingly. If a bool toggle is set, I also want it to force NumLock on:
bool NumLock = (((ushort)GetKeyState(0x90)) & 0xffff) != 0;
if (NumLock)
{
this.Dispatcher.Invoke(() =>
{
fixerBoxes["NumL"].FixerImg.Source = new BitmapImage(new Uri(@"/graphics/num_lock_on.png", UriKind.Relative));
});
}
else {
this.Dispatcher.Invoke(() =>
{
fixerBoxes["NumL"].FixerImg.Source = new BitmapImage(new Uri(@"/graphics/num_lock_off.png", UriKind.Relative));
});
}
if (fixers.watchNumL)
{
// Force NumLock back on
}
Here is a class (with a library) that can do this for you. the library does much more, so it's maybe a bit overkill to use just for this. The approach uses the keybd_event
function using pinvoke:
// Simulate a key press
Interop.keybd_event((byte)virtualKey,
0x45,
Interop.KEYEVENTF_EXTENDEDKEY | 0,
IntPtr.Zero);
// Simulate a key release
Interop.keybd_event((byte)virtualKey,
0x45,
Interop.KEYEVENTF_EXTENDEDKEY | Interop.KEYEVENTF_KEYUP,
IntPtr.Zero);
Pressing and releasing the button changes the state of the LED. virtualKey
is one of the VK_ constants.
Here are the declarations:
internal partial class Interop
{
public static int VK_NUMLOCK = 0x90;
public static int VK_SCROLL = 0x91;
public static int VK_CAPITAL = 0x14;
public static int KEYEVENTF_EXTENDEDKEY = 0x0001; // If specified, the scan code was preceded by a prefix byte having the value 0xE0 (224).
public static int KEYEVENTF_KEYUP = 0x0002; // If specified, the key is being released. If not specified, the key is being depressed.
[DllImport("User32.dll", SetLastError = true)]
public static extern void keybd_event(
byte bVk,
byte bScan,
int dwFlags,
IntPtr dwExtraInfo);
[DllImport("User32.dll", SetLastError = true)]
public static extern short GetKeyState(int nVirtKey);
[DllImport("User32.dll", SetLastError = true)]
public static extern short GetAsyncKeyState(int vKey);
}
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