SendInput and 64bits

Question

Below is an extract of some code I am using to simulate key presses via the SendInput API. This works correctly if I set my application to compile for an x86 CPU, but doesn't work for x64 CPU compilation.

I'm guessing it has something todo with the fact that x64 uses double size pointers, but I tried to change this [FieldOffset(4)] to this [FieldOffset(8)] but it didn't work.

Could it be something to do with the fact it is importing the 32bit version of user32.dll?

    #region SendInput API

    [DllImport("user32.dll", EntryPoint = "SendInput", SetLastError = true)]
    static extern uint SendInput(uint nInputs, INPUT[] pInputs, int cbSize);

    [DllImport("user32.dll", EntryPoint = "GetMessageExtraInfo", SetLastError = true)]
    static extern IntPtr GetMessageExtraInfo();

    private enum KeyEvent
    {
        KeyUp = 0x0002,
        KeyDown = 0x0000,
        ExtendedKey = 0x0001
    }

    private struct KEYBDINPUT
    {
        public ushort wVk;
        public ushort wScan;
        public uint dwFlags;
        public long time;
        public uint dwExtraInfo;
    };

    [StructLayout(LayoutKind.Explicit, Size = 28)]
    private struct INPUT
    {
        [FieldOffset(0)]
        public uint type;
        [FieldOffset(4)]
        public KEYBDINPUT ki;
    };

    #endregion

    public void sendKey(KeyCode Key)
    {
        INPUT[] InputList = new INPUT[2];

        INPUT keyInput = new INPUT();
        keyInput.type = 1;

        keyInput.ki.wScan = 0;
        keyInput.ki.time = 0;
        keyInput.ki.dwFlags = (int)KeyEvent.KeyDown;
        keyInput.ki.dwExtraInfo = (uint)GetMessageExtraInfo();
        keyInput.ki.wVk = (ushort)Key;

        InputList[0] = keyInput;

        keyInput.ki.dwFlags = (int)KeyEvent.KeyUp;

        InputList[1] = keyInput;

        SendInput((uint)2, InputList, Marshal.SizeOf(InputList[0]));
    }

user_1237786 · Answer

The only thing to change for the 64bit platforms is the FieldOffset(8) (instead of 4) of the INPUT's second parameter. There is no need to change or specify sizes for the rest structures. This is enough and complete (note that I use the default InputUnion structure instead of KEYBDINPUT whereas makes no difference):

 [StructLayout(LayoutKind.Explicit)]
    public struct INPUT
    {
    [FieldOffset(0)] public uint Type;
    [FieldOffset(8)] public InputUnion U;
    }

    [StructLayout(LayoutKind.Explicit )]
    public struct InputUnion
    {
        [FieldOffset(0)] public MOUSEINPUT mi;
        [FieldOffset(0)] public KEYBDINPUT ki;
        [FieldOffset(0)] public HARDWAREINPUT hi;
    }


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


    [StructLayout(LayoutKind.Sequential)]
    public struct KEYBDINPUT
{
    public UInt16 Vk;
    public UInt16 Scan;
    public UInt32 Flags;
    public UInt32 Time;
    public IntPtr ExtraInfo;
}

    [StructLayout(LayoutKind.Sequential)]
    public struct HARDWAREINPUT
    {
        public uint uMsg;
        public ushort wParamL;
        public ushort wParamH;
    }

SendInput and 64bits

3 Answers