一个listbox控件无法显示，高手帮小弟我看看

一个listbox控件无法显示，高手帮我看看。 - C++ Builder / Windows SDK/API
#include <windows.h>

LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
  PSTR szCmdLine, int iCmdShow)
  {
  static char szAppName[] = "BtnLook" ;
  HWND hwnd ;
  MSG msg ;
  WNDCLASSEX wndclass ;

wndclass.cbSize = sizeof (wndclass) ;
  wndclass.style = CS_HREDRAW | CS_VREDRAW ;
  wndclass.lpfnWndProc = WndProc ;
  wndclass.cbClsExtra = 0 ;
  wndclass.cbWndExtra = 0 ;
  wndclass.hInstance = hInstance ;
  wndclass.hIcon = LoadIcon (NULL, IDI_APPLICATION) ;
  wndclass.hCursor = LoadCursor (NULL, IDC_ARROW) ;
  wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;
  wndclass.lpszMenuName = NULL ;
  wndclass.lpszClassName = szAppName ;
wndclass.hIconSm = LoadIcon (NULL, IDI_APPLICATION) ;

  RegisterClassEx (&wndclass) ;

  hwnd = CreateWindow (szAppName, "listbox",
  WS_OVERLAPPEDWINDOW,
  CW_USEDEFAULT, CW_USEDEFAULT,
  CW_USEDEFAULT, CW_USEDEFAULT,
  NULL, NULL, hInstance, NULL) ;

  ShowWindow (hwnd, iCmdShow) ;
  UpdateWindow (hwnd) ;

  while (GetMessage (&msg, NULL, 0, 0))
  {
  TranslateMessage (&msg) ;
  DispatchMessage (&msg) ;
  }
  return msg.wParam ;
  }

LRESULT CALLBACK WndProc (HWND hwnd, UINT iMsg, WPARAM wParam, LPARAM lParam)
{
static HWND hwnda;
  switch (iMsg)
  {
static int a,b;
a=LOWORD(GetDialogBaseUnits());
b=HIWORD(GetDialogBaseUnits());
  case WM_CREATE :
hwnda=CreateWindow("listbox",NULL,
WS_CHILD|WS_VISIBLE|LBS_STANDARD,
  0,0,a*30,b*5,hwnd,(HMENU)0,
(HINSTANCE)GetWindowLong(hwnd,GWL_HINSTANCE),
NULL);
  SendMessage(hwnda,LB_ADDSTRING,0,(LPARAM)TEXT("1"));
  return 0 ;

  case WM_SIZE :
   
  return 0 ;

  case WM_PAINT :
   
  return 0 ;

   
  case WM_COMMAND :
{
if(LOWORD(wParam)==0)
{
  int i=SendMessage(hwnda,LB_GETCURSEL,0,0);
switch(i)
{
case 0:
MessageBox(hwnd,TEXT(""),TEXT(""),MB_OK);
break;
}
 
}
  break ;
}
  case WM_DESTROY :
  PostQuitMessage (0) ;
  return 0 ;
  }
  return DefWindowProc (hwnd, iMsg, wParam, lParam) ;
  }
一个listbox控制不知为何无法显示控件，程序可以运行通过。

[解决办法]
switch里面的这三句：
static int a,b;
a=LOWORD(GetDialogBaseUnits());
b=HIWORD(GetDialogBaseUnits());

是执行不到的。放到WM_CREATE的case中。如：

C/C++ code

case WM_CREATE:    static int a, b;    a = LOWORD(GetDialogBaseUnits());    b = HIWORD(GetDialogBaseUnits());    hwnda = CreateWindow("listbox"......