Any Hotkey I want to register seems to already be taken

Question

I am trying to register a global hotkey in Visual c# 2012, build target framework .NET3, after using http://www.dreamincode.net/forums/topic/180436-global-hotkeys/ as a tutorial, I got the following (abbreviated) files:

GlobalHotkey.cs

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

namespace barcodelabel
{
    public class GlobalHotkey
    {
        private int modifier;
        private int key;
        private IntPtr hWnd;
        private int id;

        public GlobalHotkey(int modifier, Keys key, Form form)
        {
            this.modifier = modifier;
            this.key = (int)key;
            this.hWnd = form.Handle;
            id = this.GetHashCode();
        }

        public bool Register()
        {
            return RegisterHotKey(hWnd, id, modifier, key);
        }

        public bool Unregister()
        {
            return UnregisterHotKey(hWnd, id);
        }

        public override int GetHashCode()
        {
            return modifier ^ key ^ hWnd.ToInt32();
        }

        [DllImport("user32.dll")]
        private static extern bool RegisterHotKey(IntPtr hWnd, int id, int fsModifiers, int vk);

        [DllImport("user32.dll")]
        private static extern bool UnregisterHotKey(IntPtr hWnd, int id);
    }
}

GlobalHotkeyConstants.cs

using System;
using System.Collections.Generic;
using System.Text;

namespace barcodelabel
{
    class GlobalHotkeyConstants
    {
        public const int NOMOD = 0x0000;
        public const int ALT = 0x0001;
        public const int CTRL = 0x0002;
        public const int SHIFT = 0x0004;
        public const int WIN = 0x0008;

        //windows message id for hotkey
        public const int WM_HOTKEY_MSG_ID = 0x0312;

    }
}

My Form1.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Windows;
using System.Windows.Forms;
using System.Runtime.InteropServices;
using Microsoft.Win32;

namespace barcodelabel
{
    public partial class Form1 : Form
    {

        private GlobalHotkey ghk;

         protected override void WndProc(ref Message m)
        {
            if (m.Msg == GlobalHotkeyConstants.WM_HOTKEY_MSG_ID) {
                MessageBox.Show("HOTKEY PRESSED");

            }
            base.WndProc(ref m);
        }

       public Form1()
       {
           InitializeComponent();
           this.ghk = new GlobalHotkey(GlobalHotkeyConstants.SHIFT,  Keys.F10, this);
       }

       private void Form1_Load(object sender, EventArgs e)
       {
           if (!this.ghk.Register()) 
           {
               MessageBox.Show("Hotkey could not be registered");
           }
       }

       private void Form1_FormClosing(object sender, FormClosingEventArgs e)
       {
           this.ghk.Unregister();
       }
   }

No matter what hotkey I want to choose, it can not be registered. I tried using Hotkey Explorer from http://hkcmdr.anymania.com/ to check if the hotkey already was taken, but it only told me it was free.

What can I do to solve this?

This code has many deep flaws. Keep looking for something better. — Hans Passant, Jul 22 '14 at 13:48
Hi Hans ... can you give me a hint where these flaws are so I can identify "better ways"? — ty812, Jul 22 '14 at 13:50
Using a hash for the id is nonsense, a hash collision produces undiagnosable failure. Just use a counter. The pinvoke declarations are wrong, SetLastError = true is necessary to provide a decent error message when the code fails. Not throwing a Win32Exception when a winapi call fails makes failure very hard to diagnose. There is no hint at all that this code needs to be called from the form's OnHandleCreated() override. Which certainly *can* run multiple times, your hotkey simply stops working when it does. — Hans Passant, Jul 22 '14 at 13:57

score 3 · Accepted Answer · answered Jul 22 '14 at 13:37

3

I've wrote down your code in my VS and it worked properly. If you want to find the error, don't check a Boolean returned form API only. if it returns False, try using GetLastError API. Then you will have an error code. Refer to MSDN and get the error's description.

answered Jul 22 '14 at 13:37

Mohammad Mirmostafa

1,439
1
13
26

Thank you so very much for that hint... Turns out I tried using a window handle that did not exist at that time. After moving the "new GlobalHotkey" line to Form1_Load, it works like a charm. – ty812 Jul 22 '14 at 13:47

Any Hotkey I want to register seems to already be taken

1 Answers1