http://blog.youkuaiyun.com/kinglimy/article/details/6452239
在复选框中添加CComboBox变量c后会在以dlg为后缀的类中生成一个CComboBox c;
所以可在dlg类的virtual BOOL OnInitDialog();函数中初始化复选框
c.AddString(L"china");
c.AddString(L"usa");
c.AddString(L"brazil");
c.InsertString(0, L"france");
//CComboBox *pComboBox=NULL;
//pComboBox->GetDlgItem(IDC_COMBO1);
c.SetCurSel(0); //设置显示默认选项