程序代码：

void Main_OnCommand(HWND hwnd, int id, HWND hwndCtl, UINT codeNotify)
{
    switch(id)
    {
        case IDC_OK:
        {
            TCHAR STR1[256];
            TCHAR STR2[256];
           
            GetDlgItemText(hwnd,IDC_EDIT1,STR1,sizeof(STR1));
            GetDlgItemText(hwnd,IDC_EDIT2,STR2,sizeof(STR2));
            int i1=atoi(STR1);
            int i2=atoi(STR2);
            int i3;
           
            HWND hwndcombo1=GetDlgItem(hwnd,IDC_COMBO1);
            int  cursel=ComboBox_GetCurSel(hwndcombo1);
             switch(cursel)
             {
             case  0:   { i3=i1+i2;}break;
             case  1:   { i3=i1-i2;}break;
             case  2:   { i3=i1*i2;}break;
             case  3:   { i3=i1/i2;}break;

             }
            TCHAR  STR3[256];
            wsprintf(STR3,"%d",i3);
            SetDlgItemText(hwnd,IDC_EDIT3,STR3);

            


       
        }
        break;
        default:
        break;
    }
}