【C#】【SHARE】The registering of global hotkeys

I remember that when I was still using VB6 sereval years ago, if global hotkeys are required, a massive system-hooking program would be used.

That's terrible,wasn't it? :)

But in C#, this can be much easier.We can use system api : RegisterHotKey and UnregisterHotKey(This links to the official document of Microsoft)

What to do next? Certianly is to encapsulate those function into a class in order to use it rapidly.(Thanks for Sir.bomo for his template,this is his page) 

In the following class , the function ProcessKey is of great importance.

In the main form-class, a (void)  (WndProc(ref Message m)) is required,which used to processing the hotkey sends in.

Mention：The class (keys) is in (System.Windows.Forms), so surprising.

Code:(After you register the hotkey,press Ctrl+Alt+S to hide/show you window.)

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Runtime;
using System.Runtime.InteropServices;
using System.Diagnostics;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        HotKeys h = new HotKeys();

        public Form1()
        {
            InitializeComponent();
        }

        private void btnRegist_Click(object sender, EventArgs e)
        {
            if (h.Regist(this.Handle, (int)HotKeys.HotkeyModifiers.Shift + (int)HotKeys.HotkeyModifiers.Control, Keys.S, CallBack))
                MessageBox.Show("Success");
            else MessageBox.Show("Failed");
        }
        private void btnUnregist_Click(object sender, EventArgs e)
        {
            if (h.UnRegist(this.Handle, CallBack))
                MessageBox.Show("Success");
            else MessageBox.Show("Failed");
        }

        protected override void WndProc(ref Message m)
        {
            h.ProcessHotKey(m);  //Processing
            base.WndProc(ref m);
        }

        public void CallBack()
        {
            this.Visible = !this.Visible;
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }


        
    }


    public class HotKeys
    {

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


        private int keyid = 10;     
        private Dictionary<int, HotKeyCallBackHanlder> keymap = new Dictionary<int, HotKeyCallBackHanlder>();   
        public delegate void HotKeyCallBackHanlder();
        private const int WM_HOTKEY = 0x312;

        public enum HotkeyModifiers
        {
            Alt = 1,
            Control = 2,
            Shift = 4,
            Win = 8
        }

        public bool Regist(IntPtr hWnd, int modifiers, Keys vk, HotKeyCallBackHanlder callBack)  //Regist Hotkey
        {
            try
            {
                int id = keyid++;
                if (!RegisterHotKey(hWnd, id, modifiers, vk)) return false;
                keymap[id] = callBack;
            }
            catch { return false; }  //make the class stronger
            return true;
        }

        public bool UnRegist(IntPtr hWnd, HotKeyCallBackHanlder callBack)  //UnRegister hotkey
        {
            bool bx = false;
            foreach (KeyValuePair<int, HotKeyCallBackHanlder> var in keymap)
            {
                if (var.Value == callBack)
                {
                    try
                    {
                        UnregisterHotKey(hWnd, var.Key);
                        keymap.Remove(var.Key);  //I think this line is important,which the original author not add.
                    }
                    catch { }
                    bx = true;
                }
            }
            return bx;
            
        }

        public void ProcessHotKey(Message m)   //Processing and React
        {
            if (m.Msg == WM_HOTKEY) //The original author puts 0x312 here.WM_HOTKEY can be clearer.
            {
                int id = m.WParam.ToInt32();
                HotKeyCallBackHanlder callback;
                if (keymap.TryGetValue(id, out callback))
                    callback();
            }
        }
    }
}