Blocking keyboard input to external application

Question

I am creating a bot program that opens an external application and does a series of keyboard commands. Unfortunately, the user can press a keyboard button while it is botting and get it out of sequence. Is there a way to disable the keyboard for that application only? The only thing I have found is BlockInput which does not work:

[DllImport("user32.dll", EntryPoint = "BlockInput")]
[return: MarshalAs(UnmanagedType.Bool)]
public static extern bool BlockInput([MarshalAs(UnmanagedType.Bool)] bool fBlockIt);

    private void button_Click(object sender, EventArgs e)
    {
        BlockInput(true);
        //Open application and do macro
        BlockInput(false);
    }

EDIT: So I found a solution that worked better than what I asked for. I'm not answer my own question though because I didn't block JUST the external application; I was able to block all mouse and keyboard commands to the computer.

What I did was right-clicked on the Namespace under the Solution in Solution Explorer and selected Add > New Item. Add an Application Manifest File. Click on the newly created app.manifest file. Read the green that says to replace the requestedExecutionLevel and replace the current one with "requireAdministrator". Add the following code to the program:

    [DllImport("user32.dll", SetLastError = true)]
    static extern bool BlockInput(bool fBlockIt);

    private void button_Click(object sender, EventArgs e)
    {
        BlockInput(true);
        //Blocked code
        BlockInput(false);
    }

Answer 1

I find a good topic on that subject test if it fit you : How to intercept all the keyboard events and prevent losing focus in a WinForms application? (test the return -1 on the call back). The code of the link :

using System;
using System.Diagnostics;
using System.Windows.Forms;
using System.Runtime.InteropServices;

class InterceptKeys
{
private const int WH_KEYBOARD_LL = 13;
private const int WM_KEYDOWN = 0x0100;
private static LowLevelKeyboardProc _proc = HookCallback;
private static IntPtr _hookID = IntPtr.Zero;

public static void Main()
{
    _hookID = SetHook(_proc);
    Application.Run();
    UnhookWindowsHookEx(_hookID);
}

private static IntPtr SetHook(LowLevelKeyboardProc proc)
{
    using (Process curProcess = Process.GetCurrentProcess())
    using (ProcessModule curModule = curProcess.MainModule)
    {
        return SetWindowsHookEx(WH_KEYBOARD_LL, proc,
            GetModuleHandle(curModule.ModuleName), 0);
    }
}

private delegate IntPtr LowLevelKeyboardProc(
    int nCode, IntPtr wParam, IntPtr lParam);

private static IntPtr HookCallback(
    int nCode, IntPtr wParam, IntPtr lParam)
{
    if (nCode >= 0 && wParam == (IntPtr)WM_KEYDOWN)
    {
        int vkCode = Marshal.ReadInt32(lParam);
        Console.WriteLine((Keys)vkCode);
    }
    return -1;
}

[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
private static extern IntPtr SetWindowsHookEx(int idHook,
    LowLevelKeyboardProc lpfn, IntPtr hMod, uint dwThreadId);

[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
private static extern bool UnhookWindowsHookEx(IntPtr hhk);

[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
private static extern IntPtr CallNextHookEx(IntPtr hhk, int nCode,
    IntPtr wParam, IntPtr lParam);

[DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
private static extern IntPtr GetModuleHandle(string lpModuleName);
}