Windows消息编程的窗口始终无法弹出，代码已经检察了数遍了

Windows消息编程的窗口始终无法弹出，代码已经检查了数遍了
#include<windows.h>                                          
#include<iostream>
using namespace std;

LRESULT CALLBACK WinSunProc(
HWND hwnd,
UINT uMsg,
WPARAM wParam,
LPARAM lParam
);

int WINAPI WinMain(
            HINSTANCE hInstance,        
            HINSTANCE hPrevInstance,
            LPSTR lpCmdLine, 
            int nCmdShow
)    

{
WNDCLASS wndcls;
wndcls.cbClsExtra=0;
wndcls.cbWndExtra=0;
wndcls.hbrBackground=(HBRUSH)GetStockObject(BLACK_BRUSH);
wndcls.hCursor=LoadCursor(NULL,IDC_CROSS); 
wndcls.hIcon=LoadIcon(NULL,IDI_QUESTION);
wndcls.hInstance=hInstance;
wndcls.lpfnWndProc=WinSunProc;
wndcls.lpszClassName="zy's first windows"; 
wndcls.lpszMenuName=NULL;
wndcls.style=CS_HREDRAW | CS_VREDRAW; 
RegisterClass(&wndcls); 
HWND hwnd; 
hwnd=CreateWindow("zy's first win","zy's first win",WS_OVERLAPPEDWINDOW,0,0,600,400,NULL,NULL,hInstance,NULL);
ShowWindow(hwnd,SW_SHOWNORMAL); 
UpdateWindow(hwnd); 

MSG msg;
while(GetMessage(&msg,NULL,0,0)) 
{
 TranslateMessage(&msg); 
 DispatchMessage(&msg); 
}
return 0; 
}
LRESULT CALLBACK WinSunProc( 
HWND hwnd, 
UINT uMsg,
WPARAM wParam,
LPARAM lParam
)
{
switch(uMsg)  
{
case WM_CHAR: 
char szChar[100];
sprintf(szChar,"char is %d",wParam);
MessageBox(hwnd,szChar,"zy",0 ); 
break;
case WM_LBUTTONDOWN:  
MessageBox(hwnd,"mouse clicked","zy",0);
HDC hdc;
hdc=GetDC(hwnd);
TextOut(hdc,0,50,"zy's first win",strlen("zy's first win"));
ReleaseDC(hwnd,hdc);
break;
case WM_PAINT:
HDC hDC;
PAINTSTRUCT ps;
hDC=BeginPaint(hwnd,&ps);
TextOut(hDC,0,0,"zy",strlen("zy"));
EndPaint(hwnd,&ps);
break;
case WM_CLOSE:
if(IDYES==MessageBox(hwnd,"?","zy",MB_YESNO))
{
DestroyWindow(hwnd);
}
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
    return DefWindowProc(hwnd,uMsg,wParam,lParam); 
}
return 0;
}

[解决办法]
创建的窗口和注册的窗口不是同一个 啊！
wndcls.lpszClassName="zy's first windows"; 
hwnd=CreateWindow("zy's first win","zy's first win",WS_OVERLAPPEDWINDOW,0,0,600,400,NULL,NULL,hInstance,NULL);