刚学VC++编写了一个窗口，但是关闭按钮没用，求各位大神帮忙，问题关键在WM_CLOSE消息不起作用

#include <windows.h>
#include <stdio.h>
LRESULT CALLBACK WinSunProc(
    HWND hwnd,
    UINT uMsg,
    WPARAM wParam,
    LPARAM lParam
    );

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

    WNDCLASS wndcls;
    MSG msg;
    HWND hwnd;
        wndcls.cbClsExtra=0;
        wndcls.cbWndExtra=0;
        wndcls.hbrBackground=(HBRUSH)GetStockObject(DKGRAY_BRUSH);
        wndcls.hCursor=LoadCursor(NULL,IDC_ARROW);
        wndcls.hIcon=LoadIcon(NULL,IDI_ERROR);
        wndcls.hInstance=hInstance;
        wndcls.lpfnWndProc=WinSunProc;
        wndcls.lpszClassName="SUNXIN2006";
        wndcls.lpszMenuName=NULL;
        wndcls.style=CS_HREDRAW | CS_VREDRAW;

        RegisterClass(&wndcls);

        hwnd=CreateWindow("SUNXIN2006","hello",
            WS_OVERLAPPEDWINDOW,0,0,600,400,NULL,NULL,hInstance,NULL);

        ShowWindow(hwnd,SW_SHOWNORMAL);
        UpdateWindow(hwnd);

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

}
LRESULT CALLBACK WinSunProc(
        HWND hwnd,
        UINT uMsg,
        WPARAM wParam,
        LPARAM lParam
        )
{
    switch(uMsg)
    {
    case WM_CHAR:
        char szchar[20];
        sprintf(szchar,"char code is %d",wParam);
        MessageBox(hwnd,szchar,"char",0);
        break;

    case WM_LBUTTONDOWN:
        MessageBox(hwnd,"mouse click!","message",0);
        HDC hdc;
        hdc=GetDC(hwnd);
        TextOut(hdc,0,50,"你是我的眼",strlen("你是我的眼"));
        ReleaseDC(hwnd,hdc);
        break;

    case WM_PAINT:
        HDC hDC;
        PAINTSTRUCT ps;
        hDC=BeginPaint(hwnd,&ps);
        TextOut(hDC,0,80,"我是周方武",strlen("我是周方武"));
        EndPaint(hwnd,&ps);
        break;

    case WM_CLOSE:
        DestroyWindow(hwnd);
        
        break;

    //    if (IDYES==MessageBox(hwnd,"是否真的要关闭程序？","message",MB_YESNO))
    //    {
        
    //    }
   

    case WM_DESTROY:
        PostQuitMessage(0);
        break;
    default:
        return DefWindowProc(hwnd,uMsg,wParam,lParam);
    }
    return 0;
}