.net difference between right shift and left shift keys

Question

I am currently working on an application which requires different behaviour based on whether the user presses the right or left shift key (RShiftKey, LShiftKey), however whe

Answer 1

Thanks guys, good solution there. In the mean time here's my own "hacky" way of doing it from the override of ProcessCmdKey:

public override bool ProcessCmdKey(ref Message msg, Keys keyData)
{
    if (msg.LParam.ToInt32() == 0x2a0001)
        LastShiftKey = ShiftKeys.NumericShift;
        else if (msg.LParam.ToInt32() == 0x360001)
            LastShiftKey = ShiftKeys.AlphaShift;
    etc....
}

Answer 2

I had a similar need to differentiate between the left and right shift and control keys. Here's my rather-longer but possibly better solution. If you want to catch the alt keys, you'll need to override some other things to prevent them from activating any menu(s). ((int)m.LParam & 0xFFFF) should give the repeat count, but it never seems to go above 2.

    protected override bool ProcessKeyMessage(ref Message m)
    {
        if ((m.Msg == WM_KEYDOWN || m.Msg == WM_KEYUP) && ((int)m.WParam == VK_CONTROL || (int)m.WParam == VK_SHIFT))
        {
           KeyEventArgs e = new KeyEventArgs(Keys.None);
           switch ((OemScanCode)(((int)m.LParam >> 16) & 0x1FF))
            {
                case OemScanCode.LControl:
                    e = new KeyEventArgs(Keys.LControlKey);
                    break;
                case OemScanCode.RControl:
                    e = new KeyEventArgs(Keys.RControlKey);
                    break;
                case OemScanCode.LShift:
                    e = new KeyEventArgs(Keys.LShiftKey);
                    break;
                case OemScanCode.RShift:
                    e = new KeyEventArgs(Keys.RShiftKey);
                    break;
                default:
                    if ((int)m.WParam == VK_SHIFT)
                        e = new KeyEventArgs(Keys.ShiftKey);
                    else if ((int)m.WParam == VK_CONTROL)
                        e = new KeyEventArgs(Keys.ControlKey);
                    break;
            }
            if (e.KeyData != Keys.None)
            {
                if (m.Msg == WM_KEYDOWN)
                    OnKeyDown(e);
                else
                    OnKeyUp(e);
                return true;
            }
        }
        return base.ProcessKeyMessage(ref m);
    }

    #region Scan code & window message stuff
    const int WM_KEYDOWN = 0x100;
    const int WM_KEYUP = 0x101;

    const int VK_SHIFT = 0x10;
    const int VK_CONTROL = 0x11;
    /// <summary>
    /// Alt key
    /// </summary>
    const int VK_MENU = 0x12;

    /// <summary>
    /// List of scan codes for standard 104-key keyboard US English keyboard
    /// </summary>
    enum OemScanCode
    {
        /// <summary>
        /// ` ~
        /// </summary>
        BacktickTilde = 0x29,
        /// <summary>
        /// 1 !
        /// </summary>
        N1 = 2,
        /// <summary>
        /// 2 @
        /// </summary>
        N2 = 3,
        /// <summary>
        /// 3 #
        /// </summary>
        N3 = 4,
        /// <summary>
        /// 4 $
        /// </summary>
        N4 = 5,
        /// <summary>
        /// 5 %
        /// </summary>
        N5 = 6,
        /// <summary>
        /// 6 ^
        /// </summary>
        N6 = 7,
        /// <summary>
        /// 7 &
        /// </summary>
        N7 = 8,
        /// <summary>
        /// 8 *
        /// </summary>
        N8 = 9,
        /// <summary>
        /// 9 (
        /// </summary>
        N9 = 0x0A,
        /// <summary>
        /// 0 )
        /// </summary>
        N0 = 0x0B,
        /// <summary>
        /// - _
        /// </summary>
        MinusDash = 0x0C,
        /// <summary>
        /// = +
        /// </summary>
        Equals = 0x0D,
        Backspace = 0x0E,
        Tab = 0x0F,
        Q = 0x10,
        W = 0x11,
        E = 0x12,
        R = 0x13,
        T = 0x14,
        Y = 0x15,
        U = 0x16,
        I = 0x17,
        O = 0x18,
        P = 0x19,
        /// <summary>
        /// [ {
        /// </summary>
        LBracket = 0x1A,
        /// <summary>
        /// ] }
        /// </summary>
        RBracket = 0x1B,
        /// <summary>
        /// | \ (same as pipe)
        /// </summary>
        VerticalBar = 0x2B,
        /// <summary>
        /// | \ (same as vertical bar)
        /// </summary>
        Pipe = 0x2B,
        CapsLock = 0x3A,
        A = 0x1E,
        S = 0x1F,
        D = 0x20,
        F = 0x21,
        G = 0x22,
        H = 0x23,
        J = 0x24,
        K = 0x25,
        L = 0x26,
        /// <summary>
        /// ; :
        /// </summary>
        SemiColon = 0x27,
        /// <summary>
        /// ' "
        /// </summary>
        Quotes = 0x28,
        // Unused
        Enter = 0x1C,
        LShift = 0x2A,
        Z = 0x2C,
        X = 0x2D,
        C = 0x2E,
        V = 0x2F,
        B = 0x30,
        N = 0x31,
        M = 0x32,
        /// <summary>
        /// , <
        /// </summary>
        Comma = 0x33,
        /// <summary>
        /// . >
        /// </summary>
        Period = 0x34,
        /// <summary>
        /// / ?
        /// </summary>
        Slash = 0x35,
        RShift = 0x36,
        LControl = 0x1D,
        LAlternate = 0x38,
        SpaceBar = 0x39,
        RAlternate = 0x138,
        RControl = 0x11D,
        /// <summary>
        /// The menu key thingy
        /// </summary>
        Application = 0x15D,
        Insert = 0x152,
        Delete = 0x153,
        Home = 0x147,
        End = 0x14F,
        PageUp = 0x149,
        PageDown = 0x151,
        UpArrow = 0x148,
        DownArrow = 0x150,
        LeftArrow = 0x14B,
        RightArrow = 0x14D,
        NumLock = 0x145,
        NumPad0 = 0x52,
        NumPad1 = 0x4F,
        NumPad2 = 0x50,
        NumPad3 = 0x51,
        NumPad4 = 0x4B,
        NumPad5 = 0x4C,
        NumPad6 = 0x4D,
        NumPad7 = 0x47,
        NumPad8 = 0x48,
        NumPad9 = 0x49,
        NumPadDecimal = 0x53,
        NumPadEnter = 0x11C,
        NumPadPlus = 0x4E,
        NumPadMinus = 0x4A,
        NumPadAsterisk = 0x37,
        NumPadSlash = 0x135,
        Escape = 1,
        PrintScreen = 0x137,
        ScrollLock = 0x46,
        PauseBreak = 0x45,
        LeftWindows = 0x15B,
        RightWindows = 0x15C,
        F1 = 0x3B,
        F2 = 0x3C,
        F3 = 0x3D,
        F4 = 0x3E,
        F5 = 0x3F,
        F6 = 0x40,
        F7 = 0x41,
        F8 = 0x42,
        F9 = 0x43,
        F10 = 0x44,
        F11 = 0x57,
        F12 = 0x58,
    }
    #endregion

Answer 3

Take a look at the GetAsyncKeyState Win32 method. You can add a pInvoke call to it using:

[DllImport("user32.dll")]
private static extern short GetAsyncKeyState(Keys key);

and then handle the KeyDown event on your form:

private void MyForm_KeyDown(object sender, KeyEventArgs e)
{
    Console.WriteLine("Left Shift :  " + (GetAsyncKeyState(Keys.LShiftKey) < 0));
    Console.WriteLine("Right Shift: " + (GetAsyncKeyState(Keys.RShiftKey) < 0));
}

Answer 4

I don't know if this post will help you or not, but it looks like you may have to mess with InteropServices and Diagnostics:

MSDN Forum: How to send Left/Right shift key

Edit: I finally figured out how to make GetAsyncKeyState() work, as adrianbanks revealed.

[System.Runtime.InteropServices.DllImport("user32.dll")]
private static extern short GetAsyncKeyState(Keys vKey);

private void theForm_KeyDown(object sender, KeyEventArgs e)
{
    if (e.KeyCode == Keys.ShiftKey)
    {
        if (Convert.ToBoolean(GetAsyncKeyState(Keys.LShiftKey)))
        {
            Console.WriteLine("Left");
        }
        if (Convert.ToBoolean(GetAsyncKeyState(Keys.RShiftKey)))
        {
            Console.WriteLine("Right");
        }
    }
}