Differentiating between different hotkeys in c#

[Luke Dyer]

Hi, I'm making a hotkey app and don't know how to know which hotkey has been pressed. Here's the relevant part of my source: My hotkey class

class Hotkey : IMessageFilter
{
    \[DllImport("user32.dll", SetLastError = true)\]
    private static extern bool RegisterHotKey(IntPtr hWnd, int id, int fsModifiers, int vlc);
    \[DllImport("user32.dll", SetLastError = true)\]
    private static extern bool UnregisterHotKey(IntPtr hWnd, int id);

    private const int WMHotkey = 0x0312;

    #region Properties
    private IntPtr \_Handle;
    public IntPtr Handle
    {
        get { return \_Handle; }
        set { \_Handle = value; }
    }
    private int \_Key;
    public int Key
    {
        get { return \_Key; }
        set
        {
            UnregisterHotkey();
            try
            {
                RegisterHotKey(value, \_Mod);
            }
            catch (Exception e)
            {
                MessageBox.Show("Could not register Hotkey  - there is probably a conflict.  " + "/br " + e.ToString(), "", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
            \_Key = value;
        }

    }
    private byte \_Mod;
    public byte Mod
    {
        get { return \_Mod; }
        set
        {
            UnregisterHotkey();
            try
            {
                RegisterHotKey(Key, value);
            }
            catch (Exception e)
            {
                MessageBox.Show("Could not register Hotkey  - there is probably a conflict.  " + "/br " + e.ToString(), "", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
            \_Mod = value;
        }

    }
    private bool \_isPressed;
    public bool isPressed
    {
        get { return \_isPressed; }
        set { \_isPressed = value; }
    } 
    #endregion

    private event EventHandler HotkeyPressed;
    // Alt = 1, Ctrl = 2, Shift = 4, Win = 8
    public Hotkey(Keys key, byte modifier, EventHandler hotKeyPressed)
    {
        if (key != Keys.None)
        {
            HotkeyPressed = hotKeyPressed;
            try
            {
                RegisterHotKey(CharCodeFromKeys(key), modifier);
            }
            catch (Exception e)
            {

[Luc Pattyn]

Hi, the id parameter in RegisterHotkey must be unique (your _Mod is not good); it is used internally to discriminate the different hotkeys; I once used the following code:

int chr=(int)name\[0\];
if (chr>=(int)'a' && chr<=(int)'z') chr+=(int)'A'-(int)'a';
// identifier must be unique, so we use a hash code
int ident=GetType().GetHashCode()+(modifiers<<16)+chr;

but that is just one attempt to get unique numbers for some command based on its name (some textual description) and the modifier keys (similar to Control.ModifierKeys) all inside a form. :)

Luc Pattyn

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