Can not close a message box

 #include "stdafx.h"
#include "testdlg.h"
 
#define MAX_LOADSTRING 100
 
// 全局变量:
HINSTANCE hInst;                                // 当前实例
TCHAR szTitle[MAX_LOADSTRING];                  // 标题栏文本
TCHAR szWindowClass[MAX_LOADSTRING];            // 主窗口类名
 
BOOL                InitInstance(HINSTANCE, int);
INT_PTR CALLBACK    WndProc(HWND, UINT, WPARAM, LPARAM);
INT_PTR CALLBACK    About(HWND, UINT, WPARAM, LPARAM);
 
int APIENTRY _tWinMain(HINSTANCE hInstance,
                     HINSTANCE hPrevInstance,
                     LPTSTR    lpCmdLine,
                     int       nCmdShow)
{
    UNREFERENCED_PARAMETER(hPrevInstance);
    UNREFERENCED_PARAMETER(lpCmdLine);
 
    MSG msg;
 
    if (!InitInstance (hInstance, nCmdShow))
    {
        return FALSE;
    }
 
    // 主消息循环:
    while (GetMessage(&msg, NULL, 0, 0))
    {
        if (!IsDialogMessage(msg.hwnd,&msg))
        {
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }
    }
 
    return (int) msg.wParam;
}
 
 
BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
{
   HWND hWnd;
 
   hInst = hInstance; // 将实例句柄存储在全局变量中
 
   hWnd =CreateDialog(hInstance,MAKEINTRESOURCE(IDD_DIALOG1),NULL,WndProc);
 
   if (!hWnd)
   {
      return FALSE;
   }
 
   ShowWindow(hWnd, nCmdShow);
   UpdateWindow(hWnd);
 
   return TRUE;
}
 
INT_PTR CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    int wmId, wmEvent;
    PAINTSTRUCT ps;
    HDC hdc;
 
    switch (message)
    {
    case WM_COMMAND:
        wmId    = LOWORD(wParam);
        wmEvent = HIWORD(wParam);

        switch (wmId)
        {
        case IDOK:
            MessageBox(hWnd,_T("can no close!"),_T("confused!"),MB_OK);
            break;
        case IDCANCEL:
            DestroyWindow(hWnd);
            break;
        default:
            return DefWindowProc(hWnd, message, wParam, lParam);
        }
        break;
    case WM_PAINT:
        hdc = BeginPaint(hWnd, &ps);

        EndPaint(hWnd, &ps);
        break;
    case WM_DESTROY:
        PostQuitMessage(0);
        break;
    default:
        return DefWindowProc(hWnd, message, wParam, lParam);
    }
    return 0;
}