Scrolling Notepad using C# and WIN32

Question

I'm trying to scroll a Notepad window using a C# application. The relevant code block is below, the call to move/size the window works so I know the handle is valid

please can you see what I am missing nothing happens when this is run.

    [Flags]
    public enum SetWindowPosFlags : uint
    {
        SWP_ASYNCWINDOWPOS = 0x4000,
        SWP_DEFERERASE = 0x2000,
        SWP_DRAWFRAME = 0x0020,
        SWP_FRAMECHANGED = 0x0020,
        SWP_HIDEWINDOW = 0x0080,
        SWP_NOACTIVATE = 0x0010,
        SWP_NOCOPYBITS = 0x0100,
        SWP_NOMOVE = 0x0002,
        SWP_NOOWNERZORDER = 0x0200,
        SWP_NOREDRAW = 0x0008,
        SWP_NOREPOSITION = 0x0200,
        SWP_NOSENDCHANGING = 0x0400,
        SWP_NOSIZE = 0x0001,
        SWP_NOZORDER = 0x0004,
        SWP_SHOWWINDOW = 0x0040,
    }


    private const int WM_SCROLL = 276; // Horizontal scroll
    private const int WM_VSCROLL = 277; // Vertical scroll
    private const int SB_LINEUP = 0; // Scrolls one line up
    private const int SB_LINELEFT = 0;// Scrolls one cell left
    private const int SB_LINEDOWN = 1; // Scrolls one line down
    private const int SB_LINERIGHT = 1;// Scrolls one cell right
    private const int SB_PAGEUP = 2; // Scrolls one page up
    private const int SB_PAGELEFT = 2;// Scrolls one page left
    private const int SB_PAGEDOWN = 3; // Scrolls one page down
    private const int SB_PAGERIGTH = 3; // Scrolls one page right
    private const int SB_PAGETOP = 6; // Scrolls to the upper left
    private const int SB_LEFT = 6; // Scrolls to the left
    private const int SB_PAGEBOTTOM = 7; // Scrolls to the upper right
    private const int SB_RIGHT = 7; // Scrolls to the right
    private const int SB_ENDSCROLL = 8; // Ends scroll


    [DllImport("user32.dll", CharSet = CharSet.Auto)]
    private static extern IntPtr SendMessage(IntPtr hWnd, int Msg, IntPtr wParam, IntPtr lParam);

    [DllImport("user32.dll")]
    [return: MarshalAs(UnmanagedType.Bool)]
    static extern bool SetWindowPos(IntPtr hWnd, IntPtr hWndInsertAfter, int X, int Y, int cx, int cy, SetWindowPosFlags uFlags);



    public void scroll()
    {


        IntPtr handle = IntPtr.Zero;

        Process[] processes = Process.GetProcessesByName("Notepad");

        foreach (Process p in processes)
        {
            handle = p.MainWindowHandle;

            Console.WriteLine("Got Handle: " + p.MainWindowTitle);

            break;
        }

        //this is to test I have a valid handle
        SetWindowPos(handle, new IntPtr(0), 10, 10, 1024, 350, SetWindowPosFlags.SWP_DRAWFRAME);


        SendMessage(handle, WM_VSCROLL,  (IntPtr)SB_LINEDOWN, IntPtr.Zero);
        SendMessage(handle, WM_VSCROLL, (IntPtr)SB_PAGEDOWN, IntPtr.Zero);

    }

Answer 1

This fails because you are sending the WM_VSCROLL message to the main window. You need to send the message to Notepad's edit control, which is the window with the scrollbar.

You can enumerate Notepad's child windows using EnumChildWindows. The child with class "Edit" is the one you want.