In Scott Hanselman’s recent Hanselminutes podcast with Chris Sells, he bemoaned the fact that in .NET you can’t just query the keyboard state to say “is this key pressed right now?” Chris answered that you can do it, but that he’d have to look it up to get the exact reference. I got curious and looked it up myself. It turns out you can get the currently pressed mouse buttons (as a static property on the System.Windows.Forms.Form class), but you can’t retrieve the current keyboard state. Fortunately for us P/Invoke comes to the rescue. (Unless you’re trying to run in Mono.) Below is a simple console application that checks the state of a particular key (or keys) in a loop. There is a Win32 API call to get the entire keyboard state, but for the purposes of tracking one or two keys, it’s overkill.

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

namespace Lerch.KeyPressTest
{
    public class KeyPressTest
    {
        [DllImport("user32.dll")]
        public static extern ushort GetKeyState(short nVirtKey);

        public const ushort keyDownBit = 0x80;

        public static void Main(string[] args)
        {
            long counter = 0;
            while (true)
            {
                if (Form.MouseButtons == MouseButtons.Right)
                {
                    Console.WriteLine("Right mouse button detected");
                    break;
                }
                else if (IsKeyPressed(Keys.Escape))
                {
                    Console.WriteLine("Escape key detected");
                    break;
                }

                if (IsKeyPressed(Keys.Up))
                {
                    Console.WriteLine("UP {0}", counter++);
                }
                else if (IsKeyPressed(Keys.Down))
                {
                    Console.WriteLine("DOWN {0}", counter--);
                }
            }

            Console.WriteLine("Press enter to exit...");
            Console.ReadLine();
        }

        public static bool IsKeyPressed(Keys key)
        {
            return ((GetKeyState((short)key) & keyDownBit) == keyDownBit);
        }
    }
}