grok_SendInput.cs

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

[StructLayout(LayoutKind.Sequential)]
struct INPUT
{
    public uint type;
    public MOUSEINPUT mi;
}

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

const int INPUT_MOUSE = 0;
const uint MOUSEEVENTF_LEFTDOWN = 0x0002;
const uint MOUSEEVENTF_LEFTUP = 0x0004;

public static void ClickAt(int x, int y)
{
    INPUT[] input = new INPUT[2];
    input[0].type = INPUT_MOUSE;
    input[0].mi.dx = x;
    input[0].mi.dy = y;
    input[0].mi.mouseData = 0;
    input[0].mi.dwFlags = MOUSEEVENTF_LEFTDOWN;
    input[0].mi.time = 0;
    input[0].mi.dwExtraInfo = IntPtr.Zero;

    input[1].type = INPUT_MOUSE;
    input[1].mi.dx = x;
    input[1].mi.dy = y;
    input[1].mi.mouseData = 0;
    input[1].mi.dwFlags = MOUSEEVENTF_LEFTUP;
    input[1].mi.time = 0;
    input[1].mi.dwExtraInfo = IntPtr.Zero;

    SendInput((uint)input.Length, input, Marshal.SizeOf(typeof(INPUT)));
}