Using a low-level keyboard hook to change keyboard characters

Question

I\'m creating a custom keyboard layout. As the beginning step, I want to have the user press a key, have my keyboard hook intercept it, and output a different key of my choosing

Answer 1

The second parameter for Marshal.PtrToStructure must be a class not a struct and KBDLLHOOKSTRUCT is probably a struct.

Instead you should use it like this:

KBDLLHOOKSTRUCT replacementKey = (KBDLLHOOKSTRUCT)Marshal.PtrToStructure(lParam, typeof(KBDLLHOOKSTRUCT));
replacementKey.vkCode = 90; // char 'Z'
Marshal.StructureToPtr(replacementKey, lParam, false);