Win32 Runtime Created LISTBOX and LB_ADDSTRING errors

Question

I am creating a LISTBOX using the default LISTBOX class in Windows and the C language.
The Listbox is drawn onto the main window properly, but when I try to subsequently fill it with any data, it silently fails. SendMessage() returns 0 every time. The handle to the listbox has been confirmed to be proper, the LB_ADDSTRING definition is 0x0180 (which I assume is also proper).
I have tried char * and wchar_t * and literal strings, none of them will show up, all of them return 0 from SendMessage() calls no matter how many times it is called. I am left to assume that perhaps my message handler, or my class and window creation, are incorrect. Here is the most recent version of the associated code:

LRESULT CALLBACK DBWinProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    switch ( uMsg )
    {
        case WM_CREATE:
            break;
        case WM_PAINT:
            break;
        case WM_DESTROY:
            break;
        default:
            return DefWindowProc(hWnd, uMsg, wParam, lParam);
    }
    return 0;
}

void DBClassBuilder()
{
    WNDCLASSEX wc;

    memset(&wc, 0, sizeof(wc));
    wc.cbSize = sizeof(WNDCLASSEX);
    wc.lpfnWndProc = DBWinProc;
    wc.hInstance = g_pi.hInstance;
    wc.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
    wc.lpszClassName = TEXT("LISTBOX");

    if ( !RegisterClassEx(&wc) )
        return;

    g_pi.hb.hDBListBox = CreateWindowEx(
        0, TEXT("LISTBOX"),
        TEXT(""),
        WS_CHILD | LBS_HASSTRINGS | LBS_STANDARD,
        0, 0, 100, 300,
        g_pi.hWnd, NULL, g_pi.hInstance, NULL);

    if ( g_pi.hb.hDBListBox == NULL )
        return;

    SendMessage(g_pi.hb.hDBListBox, WM_SETFONT, (WPARAM)GetStockObject(DEFAULT_GUI_FONT), MAKELPARAM(FALSE,0));

    ShowWindow(g_pi.hb.hDBListBox, g_pi.nCmdShow);
    UpdateWindow(g_pi.hb.hDBListBox);
}

LRESULT CALLBACK MainWinProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    g_pi.hWnd = hWnd;
    switch ( uMsg )
    {
        case WM_CREATE:
            SaveMainPos();
            DBClassBuilder();
            SendMessage(g_pi.hb.hDBListBox, LB_ADDSTRING, 0, (LPARAM)"test");
            break;
        case WM_PAINT:
            SaveMainPos();
            UpdateChildren();
            break;
        case WM_CLOSE:
            DestroyWindow(hWnd);
            break;
        case WM_DESTROY:
            PostQuitMessage(0);
            break;
        default:
            return DefWindowProc(hWnd, uMsg, wParam, lParam);
    }
    return 0;
}

Answer 1

As you register a "LISTBOX" class yourself, your window is of that class instead of the standard listbox control class. Therefore the standard listbox window procedure is never called.

What you probably want to achieve is called subclassing, using an existing windowclass and tweaking the behavior. A web search should give you many examples of proper subclassing.