Create Window without Registering a WNDCLASS?

Question

Is it absolutely necessary to always build and register a new WNDCLASS(EX) for your application? And then use the lpszClassName for the main window?

Isn\'t there som

Answer 1

There are no pre-defined window classes for top-level application windows. You must register a window class for your application, or use a dialog.

Answer 2

You can create a mini app out of a dialog resource, you use CreateDialog() instead of CreateWindow(). Boilerplate code could look like this, minus the required error checking:

#include "stdafx.h"
#include "resource.h"

INT_PTR CALLBACK DlgProc(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
    case WM_INITDIALOG: 
        return (INT_PTR)TRUE;
    case WM_COMMAND:
        if (LOWORD(wParam) == IDOK || LOWORD(wParam) == IDCANCEL) {
            DestroyWindow(hDlg);
            PostQuitMessage(LOWORD(wParam)-1);
            return (INT_PTR)TRUE;
        }
        break;
    }
    return (INT_PTR)FALSE;
}

int APIENTRY _tWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPTSTR lpCmdLine, int nCmdShow) {
    HWND hWnd = CreateDialog(hInstance, MAKEINTRESOURCE(IDD_DIALOG1), NULL, DlgProc);
    if (hWnd == NULL) DebugBreak();
    ShowWindow(hWnd, nCmdShow);
    UpdateWindow(hWnd);
    MSG msg;
    while (GetMessage(&msg, NULL, 0, 0)) {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    return (int) msg.wParam;
}

Which assumes you created a dialog with the resource editor using id IDD_DIALOG1.