[C#]不通过事件方式获取键盘按钮按下的状态

源码来自：https://www.pinvoke.net/default.aspx/user32/GetKeyboardState.html

以前，如果想获取键盘按钮是否被按下，一般通过键盘事件去获取，而有时候，我们可能使用的不是Windows Form，可能是控制台或类库，则不得不放弃使用键盘事件的方式，而需另找其他方法。

我们可以通过使用Win32 API中的GetKeyState函数来实现键盘按钮按下状态的检查，而不通过键盘事件方式，代码如下：

    using System;
    using System.Collections.Generic;
    using System.Runtime.InteropServices;
    using System.Text;

    namespace PInvoke.Net
    {
        public class Keyboard
        {
            [DllImport( "user32.dll" )]
            static extern short GetKeyState( VirtualKeyStates nVirtKey );

            public static bool IsKeyPressed( VirtualKeyStates testKey )
            {
                bool keyPressed = false;
                short result = GetKeyState( testKey );

                switch( result )
                {
                    case 0:
                    // Not pressed and not toggled on.
                    keyPressed = false;
                    break;

                    case 1:
                    // Not pressed, but toggled on
                    keyPressed = false;
                    break;

                    default:
                    // Pressed (and may be toggled on)
                    keyPressed = true;
                    break;
                }

                return keyPressed;
            }

            public enum VirtualKeyStates : int
            {
                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, /* old name - should be here for compatibility */
                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, // '=' key on numpad
                //
                VK_OEM_FJ_JISHO = 0x92, // 'Dictionary' key
                VK_OEM_FJ_MASSHOU = 0x93, // 'Unregister word' key
                VK_OEM_FJ_TOUROKU = 0x94, // 'Register word' key
                VK_OEM_FJ_LOYA = 0x95, // 'Left OYAYUBI' key
                VK_OEM_FJ_ROYA = 0x96, // 'Right OYAYUBI' key
                //
                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, // ';:' for US
                VK_OEM_PLUS = 0xBB, // '+' any country
                VK_OEM_COMMA = 0xBC, // ',' any country
                VK_OEM_MINUS = 0xBD, // '-' any country
                VK_OEM_PERIOD = 0xBE, // '.' any country
                VK_OEM_2 = 0xBF, // '/?' for US
                VK_OEM_3 = 0xC0, // '`~' for US
                //
                VK_OEM_4 = 0xDB, // '[{' for US
                VK_OEM_5 = 0xDC, // '\|' for US
                VK_OEM_6 = 0xDD, // ']}' for US
                VK_OEM_7 = 0xDE, // ''"' for US
                VK_OEM_8 = 0xDF,
                //
                VK_OEM_AX = 0xE1, // 'AX' key on Japanese AX kbd
                VK_OEM_102 = 0xE2, // "<>" or "\|" on RT 102-key kbd.
                VK_ICO_HELP = 0xE3, // Help key on ICO
                VK_ICO_00 = 0xE4, // 00 key on ICO
                //
                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
            }
        }
    }