出现下面两个error：我应该怎么修改？

Question

void CXDlg::Ondelete()
{
// TODO: Add your control notification handler code here
int i=m_num.GetLength();
if(i != 0)
{
m_num.Delete(i-1,1);
UpdateData(false);
}
}

出现下面两个错误：
error C2228:left of '.GetLength' must have class/struct/union type
error C2228: left of '.Delete' must have class/struct/union type
应该怎么改？

Answer 1

m_num没有定义