WindowsForms的窗体关闭

program类改成

static class Program
    {
        /// <summary>
        /// 应用程序的主入口点。
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Login login = new Login();
            login.Show();
            Application.Run();
        }
    }

//登录按钮

private void btnLogin_Click(object sender, EventArgs e)
        {
            string UIds = this.txtUser.Text.Trim().ToString();
            string UPassword = this.txtPwd.Text.Trim().ToString();
            string UTypeName = this.cbbTypeName.SelectedItem.ToString();
            if (new UserManager().AdminLogin(UIds, UPassword, UTypeName))
            {
                Login.ActiveForm.Close();
                MainForm mf = new MainForm();
                mf.Show();
            }
            else
            {
                MessageBox.Show("登入失败！");
            }
        }