无法关闭窗口！请高手帮个忙看一下啊

Question

login loginfrom = new login(); 
loginfrom.Hide();

Answer 1

if (myreader.Read()) 
            { 
                Mainfrom Mainfrom = new Mainfrom(); 
                login loginfrom = new login();
                DialogResult rs = loginfrom.ShowDialog();
                if(rs == DialogResult.OK)
                {  
                   loginfrom.Hide(); 
                   Mainfrom.Show(); 
                }
                return; 
            }