新手求助WinMain函数

#include "windows.h"
#include "stdio.h"

LRESULT CallWinSunProc(
  HWND hWnd,              // handle to window
  UINT Msg,               // message
  WPARAM wParam,          // first message parameter
  LPARAM lParam           // second message parameter
);

int WINAPI WinMain(
  HINSTANCE hInstance,  // handle to current instance
  HINSTANCE hPrevInstance,  // handle to previous instance
  LPSTR lpCmdLine,      // pointer to command line
  int nCmdShow          // show state of window
)
{
    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_ERROR);
    wndcls.hInstance=hInstance;
    wndcls.lpfnWndProc=WinSunProc;
    wndcls.lpszClassName="Weixin";
    wndcls.lpszMenuName=NULL;
    wndcls.style=CS_HREDRAW | CS_VREDRAW;
    RegisterClass(&wndcls);

    HWND hwnd;
    hwnd=CreateWindow("Weixin","北京维新科学技术培训中心",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 CallWinSunProc(
  HWND hWnd,              // handle to window
  UINT Msg,               // message
  WPARAM wParam,          // first message parameter
  LPARAM lParam           // second message parameter
)
{
    HDC hdc;
    PAINTSTRUCT ps;
    switch(uMsg)
    {
    case WM_CHAR:
        char szChar[20];
        sprintf(szChar,"char is %d",wParam);
        MessageBox(hwnd,szChar,"Weixin",0);
        break;
    case WM_LBUTTONDOWN:
        MessageBox(hwnd,"nouse clicked","Weixin",0);
        HDC hdc;
        hdc=GetDC(hwnd);
        TextOut(hdc,0,50,"计算机编程语言培训",strlen("计算机编程语言培训"));
        ReleaseDC(hwnd,hdc);
        break;
    case WM_PAINT:
        HDC hdc;
        PAINTSTRUCT ps;
        hDC=BeginPaint(hwnd,&ps);
        TextOut(hdc,0,0"维新培训",strlen("维新培训"));
        EndPaint(hwnd,&ps);
        break;
    case WM_CLOSE:
        if(IDYES==MessageBox(hwnd,"是否真的","Weixin",MB_YESNO))
        {
            DestroyWindow(hwnd);
        }
        break;
    case WM_DESTROY:
        PostQuitMessage(0);
        break;
    default:
        return DefWindowProc(hwnd,uMsg,wParam,lParam);

    }
    return 0;
}
这个我跟着孙鑫老师写的程序就一直无法通过，求教各位大侠帮忙