Detect shift key on application startup in C#/Windows Forms

问题

Is there a way to get a standard Windows Forms application to detect if the Shift key is being held down on application startup - without using Windows hooks?

I ideally would like the workflow to change from normal if the shift key is held down when the EXE file is run.

回答1:

Here is an article about reading the key states (and mouse) directly.

回答2:

The ModifierKeys property looks ideal:

private void Form1_Load(object sender, EventArgs e)
{
    if ( (ModifierKeys & Keys.Shift) != 0)
    {
      MessageBox.Show("Shift is pressed");
    }
}

回答3:

Check Control.ModifierKeys ...

    [STAThread]
    static void Main(string[] args)
    {
        if (Control.ModifierKeys == Keys.ShiftKey)
        {
            // Do something special
        }
    }

回答4:

I know this post is rather old but I ran into this issue and fixed it by modifying Jamie's code:

[STAThread]
static void Main(string[] args)
{
    if (Control.ModifierKeys.ToString() == "Shift")
    {
        // Do something special
    }
}

回答5:

I realize this is super old, but it bothered me a little bit to see people struggling with this. ModifierKeys is a bit field, so relying on .ToString() or == to see if the Shift key is pressed is, at best, unreliable and isn't the correct use of a bit field:

public enum ModifierKeys
{
    /// <summary>No modifiers are pressed.</summary>
    None = 0,

    /// <summary>The ALT key.</summary>
    Alt = 1,

    /// <summary>The CTRL key.</summary>
    Control = 2,

    /// <summary>The SHIFT key.</summary>
    Shift = 4,

    /// <summary>The Windows logo key.</summary>
    // Windows = 8, No longer leaked
}

Either none or any combination of Alt, Control, or Shift may be pressed, so the check should be:

if ((ModifierKeys & Keys.Shift) != 0)
{
    MessageBox.Show("Shift is pressed");
}

I will up-vote Dan's answer as soon as I earn the right to do so :-) .Net 4+ includes the HasFlag() method as well, but I am accustomed to bitwise operations so I haven't used it. For more information on bitwise operations, flags, (with) truth tables, and other tidbits see:

http://geekswithblogs.net/BlackRabbitCoder/archive/2010/07/22/c-fundamentals-combining-enum-values-with-bit-flags.aspx

What you see in the source is even more intriguing:

/// <devdoc>
///     Retrieves the current state of the modifier keys. This will check the
///     current state of the shift, control, and alt keys.
/// </devdoc>
public static Keys ModifierKeys {
    get {
        Keys modifiers = 0;
        // SECURITYNOTE : only let state of Shift-Control-Alt out...
        //
        if (UnsafeNativeMethods.GetKeyState((int)Keys.ShiftKey) < 0) modifiers |= Keys.Shift;
        if (UnsafeNativeMethods.GetKeyState((int)Keys.ControlKey) < 0) modifiers |= Keys.Control;
        if (UnsafeNativeMethods.GetKeyState((int)Keys.Menu) < 0) modifiers |= Keys.Alt;
        return modifiers;
    }
}

This implementation ONLY emits the state of Shift, Control, and Alt. The Windows' key state is not included.

If you want to detect the key state BEFORE a form or control is created, maybe in the Main() method, you can go crazy.

Maybe you want to to this:

if (VirtualKeyState.VK_SHIFT.IsKeyPressed())
{
    Debugger.Launch();
}

Create a simple extension method:

public static class KeyAssist
{
    public const int KEY_PRESSED = 0x8000;

    public static bool IsKeyPressed(this VirtualKeyState key) => Convert.ToBoolean(Native.GetKeyState(key) & KEY_PRESSED);
}

Import:

[DllImport("user32.dll")]
public static extern short GetKeyState(VirtualKeyState virtualKeyState);

Create the following enum (or some sub-section if you please) (from PInvoke):

public enum VirtualKeyState
{

    VK_LBUTTON = 0x01,
    VK_RBUTTON = 0x02,
    VK_CANCEL = 0x03,
    VK_MBUTTON = 0x04,
    VK_XBUTTON1 = 0x05,
    VK_XBUTTON2 = 0x06,
    VK_BACK = 0x08,
    VK_TAB = 0x09,
    VK_CLEAR = 0x0C,
    VK_RETURN = 0x0D,
    VK_SHIFT = 0x10,
    VK_CONTROL = 0x11,
    VK_MENU = 0x12,
    VK_PAUSE = 0x13,
    VK_CAPITAL = 0x14,
    VK_KANA = 0x15,
    VK_HANGEUL = 0x15,           
    VK_HANGUL = 0x15,
    VK_JUNJA = 0x17,
    VK_FINAL = 0x18,
    VK_HANJA = 0x19,
    VK_KANJI = 0x19,
    VK_ESCAPE = 0x1B,
    VK_CONVERT = 0x1C,
    VK_NONCONVERT = 0x1D,
    VK_ACCEPT = 0x1E,
    VK_MODECHANGE = 0x1F,
    VK_SPACE = 0x20,
    VK_PRIOR = 0x21,
    VK_NEXT = 0x22,
    VK_END = 0x23,
    VK_HOME = 0x24,
    VK_LEFT = 0x25,
    VK_UP = 0x26,
    VK_RIGHT = 0x27,
    VK_DOWN = 0x28,
    VK_SELECT = 0x29,
    VK_PRINT = 0x2A,
    VK_EXECUTE = 0x2B,
    VK_SNAPSHOT = 0x2C,
    VK_INSERT = 0x2D,
    VK_DELETE = 0x2E,
    VK_HELP = 0x2F,
    VK_LWIN = 0x5B,
    VK_RWIN = 0x5C,
    VK_APPS = 0x5D,
    VK_SLEEP = 0x5F,
    VK_NUMPAD0 = 0x60,
    VK_NUMPAD1 = 0x61,
    VK_NUMPAD2 = 0x62,
    VK_NUMPAD3 = 0x63,
    VK_NUMPAD4 = 0x64,
    VK_NUMPAD5 = 0x65,
    VK_NUMPAD6 = 0x66,
    VK_NUMPAD7 = 0x67,
    VK_NUMPAD8 = 0x68,
    VK_NUMPAD9 = 0x69,
    VK_MULTIPLY = 0x6A,
    VK_ADD = 0x6B,
    VK_SEPARATOR = 0x6C,
    VK_SUBTRACT = 0x6D,
    VK_DECIMAL = 0x6E,
    VK_DIVIDE = 0x6F,
    VK_F1 = 0x70,
    VK_F2 = 0x71,
    VK_F3 = 0x72,
    VK_F4 = 0x73,
    VK_F5 = 0x74,
    VK_F6 = 0x75,
    VK_F7 = 0x76,
    VK_F8 = 0x77,
    VK_F9 = 0x78,
    VK_F10 = 0x79,
    VK_F11 = 0x7A,
    VK_F12 = 0x7B,
    VK_F13 = 0x7C,
    VK_F14 = 0x7D,
    VK_F15 = 0x7E,
    VK_F16 = 0x7F,
    VK_F17 = 0x80,
    VK_F18 = 0x81,
    VK_F19 = 0x82,
    VK_F20 = 0x83,
    VK_F21 = 0x84,
    VK_F22 = 0x85,
    VK_F23 = 0x86,
    VK_F24 = 0x87,
    VK_NUMLOCK = 0x90,
    VK_SCROLL = 0x91,
    VK_OEM_NEC_EQUAL = 0x92,        
    VK_OEM_FJ_JISHO = 0x92,     
    VK_OEM_FJ_MASSHOU = 0x93,          
    VK_OEM_FJ_TOUROKU = 0x94,      
    VK_OEM_FJ_LOYA = 0x95,      
    VK_OEM_FJ_ROYA = 0x96,      
    VK_LSHIFT = 0xA0,
    VK_RSHIFT = 0xA1,
    VK_LCONTROL = 0xA2,
    VK_RCONTROL = 0xA3,
    VK_LMENU = 0xA4,
    VK_RMENU = 0xA5,
    VK_BROWSER_BACK = 0xA6,
    VK_BROWSER_FORWARD = 0xA7,
    VK_BROWSER_REFRESH = 0xA8,
    VK_BROWSER_STOP = 0xA9,
    VK_BROWSER_SEARCH = 0xAA,
    VK_BROWSER_FAVORITES = 0xAB,
    VK_BROWSER_HOME = 0xAC,
    VK_VOLUME_MUTE = 0xAD,
    VK_VOLUME_DOWN = 0xAE,
    VK_VOLUME_UP = 0xAF,
    VK_MEDIA_NEXT_TRACK = 0xB0,
    VK_MEDIA_PREV_TRACK = 0xB1,
    VK_MEDIA_STOP = 0xB2,
    VK_MEDIA_PLAY_PAUSE = 0xB3,
    VK_LAUNCH_MAIL = 0xB4,
    VK_LAUNCH_MEDIA_SELECT = 0xB5,
    VK_LAUNCH_APP1 = 0xB6,
    VK_LAUNCH_APP2 = 0xB7,
    VK_OEM_1 = 0xBA,      
    VK_OEM_PLUS = 0xBB,      
    VK_OEM_COMMA = 0xBC,      
    VK_OEM_MINUS = 0xBD,      
    VK_OEM_PERIOD = 0xBE,      
    VK_OEM_2 = 0xBF,      
    VK_OEM_3 = 0xC0,      
    VK_OEM_4 = 0xDB,      
    VK_OEM_5 = 0xDC,      
    VK_OEM_6 = 0xDD,      
    VK_OEM_7 = 0xDE,      
    VK_OEM_8 = 0xDF,
    VK_OEM_AX = 0xE1,         
    VK_OEM_102 = 0xE2,          
    VK_ICO_HELP = 0xE3,       
    VK_ICO_00 = 0xE4,       
    VK_PROCESSKEY = 0xE5,
    VK_ICO_CLEAR = 0xE6,
    VK_PACKET = 0xE7,
    VK_OEM_RESET = 0xE9,
    VK_OEM_JUMP = 0xEA,
    VK_OEM_PA1 = 0xEB,
    VK_OEM_PA2 = 0xEC,
    VK_OEM_PA3 = 0xED,
    VK_OEM_WSCTRL = 0xEE,
    VK_OEM_CUSEL = 0xEF,
    VK_OEM_ATTN = 0xF0,
    VK_OEM_FINISH = 0xF1,
    VK_OEM_COPY = 0xF2,
    VK_OEM_AUTO = 0xF3,
    VK_OEM_ENLW = 0xF4,
    VK_OEM_BACKTAB = 0xF5,
    VK_ATTN = 0xF6,
    VK_CRSEL = 0xF7,
    VK_EXSEL = 0xF8,
    VK_EREOF = 0xF9,
    VK_PLAY = 0xFA,
    VK_ZOOM = 0xFB,
    VK_NONAME = 0xFC,
    VK_PA1 = 0xFD,
    VK_OEM_CLEAR = 0xFE
}

Anyway, this is just for reference so there isn't so much guessing going on.

HTH,

Colby

来源：https://stackoverflow.com/questions/967634/detect-shift-key-on-application-startup-in-c-windows-forms

标签

winforms

detect

hotkeys

shift