C#でSendInputを使う

SendKey.cs

using System.Runtime.InteropServices;

namespace SendKey
{
    class SendKey
    {
        // ref to https://gist.github.com/romichi/4971512

        [StructLayout(LayoutKind.Sequential)]
        private struct MOUSEINPUT
        {
            public int dx;
            public int dy;
            public int mouseData;
            public int dwFlags;
            public int time;
            public int dwExtraInfo;
        };

        [StructLayout(LayoutKind.Sequential)]
        private struct KEYBDINPUT
        {
            public short wVk;
            public short wScan;
            public int dwFlags;
            public int time;
            public int dwExtraInfo;
        };

        [StructLayout(LayoutKind.Sequential)]
        private struct HARDWAREINPUT
        {
            public int uMsg;
            public short wParamL;
            public short wParamH;
        };

        [StructLayout(LayoutKind.Explicit)]
        private struct INPUT
        {
            [FieldOffset(0)]
            public int type;
            [FieldOffset(4)]
            public MOUSEINPUT no;
            [FieldOffset(4)]
            public KEYBDINPUT ki;
            [FieldOffset(4)]
            public HARDWAREINPUT hi;
        };

        [DllImport("user32.dll")]
        private extern static void SendInput(int nInputs, ref INPUT pInputs, int cbsize);
        [DllImport("user32.dll", EntryPoint = "MapVirtualKeyA")]
        private extern static int MapVirtualKey(int wCode, int wMapType);

        private const int INPUT_KEYBOARD = 1;
        private const int KEYEVENTF_KEYDOWN = 0x0;
        private const int KEYEVENTF_KEYUP = 0x2;
        private const int KEYEVENTF_EXTENDEDKEY = 0x1;

        // ref to https://docs.microsoft.com/en-us/windows/win32/inputdev/virtual-key-codes
        private const int VK_LEFT = 0x25;
        private const int VK_Z = 0x5A;

        public void Send(int key, bool isEXTEND)
        {
            /*
             * Keyを送る
             * 入力
             *     isEXTEND : 拡張キーかどうか
             */

            INPUT inp = new INPUT();

            // 押す
            inp.type = INPUT_KEYBOARD;
            inp.ki.wVk = (short)key;
            inp.ki.wScan = (short)MapVirtualKey(inp.ki.wVk, 0);
            inp.ki.dwFlags = ((isEXTEND) ? (KEYEVENTF_EXTENDEDKEY) : 0x0) | KEYEVENTF_KEYDOWN;
            inp.ki.time = 0;
            inp.ki.dwExtraInfo = 0;
            SendInput(1, ref inp, Marshal.SizeOf(inp));

            System.Threading.Thread.Sleep(100);

            // 離す
            inp.ki.dwFlags = ((isEXTEND) ? (KEYEVENTF_EXTENDEDKEY) : 0x0) | KEYEVENTF_KEYUP;
            SendInput(1, ref inp, Marshal.SizeOf(inp));
        }
    }

    class Program
    {

        static void Main()
        {
            System.Threading.Thread.Sleep(2000);
            SendKey s = new SendKey();
            const int VK_LEFT = 0x25;
            const int VK_Z = 0x5A;
            s.Send(VK_Z, false);
            s.Send(VK_LEFT, true);
        }

    }
}