求教windows编程的窗口关闭后进程占用率100%的问题!

[forester_2008]

本人初学windows编程，对windows还不是特别熟悉，自己写了个小程序，不知为什么总是关闭窗口后，CPU占用率达到100％，不知道为什么。我是按照windows书上写的 编的 啊，怎么会出现这个问题，而且我在响应WM_DESTROY消息后，调用PostQuitMessage(0)关闭了窗口了,也退出了消息循环了啊，为什么还出现这个问题？求助各位高手！！！下面是我写的程序的内容：
#include <windows.h>
LRESULT CALLBACK WndProc(HWND,UINT,WPARAM,LPARAM);
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
PSTR szCmdLine, int nCmdShow)
{
char szAppName[]="HelloWin";
HWND hwnd;
MSG msg;
WNDCLASS wndclass;
wndclass.cbClsExtra=0;
wndclass.cbWndExtra=0;
wndclass.hbrBackground=(HBRUSH)GetStockObject(WHITE_BRUSH);
wndclass.hCursor=LoadCursor(NULL,IDC_ARROW);
wndclass.hIcon=LoadIcon(NULL,IDI_APPLICATION);
wndclass.hInstance=hInstance;
wndclass.lpfnWndProc=WndProc;
wndclass.lpszClassName=szAppName;
wndclass.lpszMenuName=NULL;
wndclass.style=CS_VREDRAW|CS_HREDRAW;
if(!RegisterClass(&wndclass))
return FALSE;
hwnd=CreateWindow(szAppName,"Hello,yaojin!",WS_OVERLAPPEDWINDOW,CW_USEDEFAULT,0,
CW_USEDEFAULT,0,NULL,NULL,hInstance,NULL);
ShowWindow(hwnd,nCmdShow);
UpdateWindow(hwnd);
while(GetMessage(&msg,hwnd,0,0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return msg.wParam;
}


LRESULT CALLBACK WndProc(HWND hwnd,UINT message,WPARAM wParam,LPARAM lParam)
{
HDC hdc;
PAINTSTRUCT ps;
RECT rect;
switch(message)
{
case WM_PAINT:
hdc=BeginPaint(hwnd,&ps);
GetClientRect(hwnd,&rect);
DrawText(hdc,"Hello,windows!",-1,&rect,DT_SINGLELINE|DT_CENTER|DT_VCENTER);
EndPaint(hwnd,&ps);
return 0;

case WM_CLOSE:
if(IDYES==MessageBox(hwnd,"是否真的要退出程序?","windows!",MB_YESNO))
DestroyWindow(hwnd);
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hwnd,message,wParam,lParam);
}
return 0;
}

[superarhow]

case WM_CLOSE:
if(IDYES==MessageBox(hwnd,"是否真的要退出程序?","windows!",MB_YESNO))
DestroyWindow(hwnd);
;<<<<==== 这里
case WM_DESTROY:
PostQuitMessage(0);
break;

在“这里”加break

[一剑]

while(GetMessage(&msg,hwnd,0,0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}

---------->

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

[forester_2008]

谢谢!!

[forester_2008]

loomman(一剑）说的很对，现在没有问题了，如果设置为hwnd,程序只关闭了这个窗口，不响应这个窗口的消息了，而NULL就是把任何窗口和窗口消息循环都关闭了，呵呵．