}
        }

        // 验证用户的输入，成功返回 True，失败返回 False
        private bool ValidateInput()
        {
            if (txtLoginId.Text.Trim() == "")
            {
                MessageBox.Show("请输入用户名", "登录提示",
                    MessageBoxButtons.OK, MessageBoxIcon.Information);
                txtLoginId.Focus();
                return false;
            }
            else if (txtLoginPwd.Text.Trim() == "")
            {
                MessageBox.Show("请输入密码", "登录提示",
                    MessageBoxButtons.OK, MessageBoxIcon.Information);
                txtLoginPwd.Focus();
                return false;
            }
            else if (cboLoginType.Text.Trim() == "")
            {
                MessageBox.Show("请选择登陆类型", "登录提示",
                    MessageBoxButtons.OK, MessageBoxIcon.Information);
                cboLoginType.Focus();
                return false;
            }
            else
            {
                return true;
            }
        }

        // 验证用户是否合法
        // 传入用户名、密码、登陆类型。合法返回 True，不合法返回 False
        // messasge 参数用来记录验证失败的原因
        private bool ValidateUser(string loginId, string loginPwd,
                             string loginType, ref string message)
        {
            if (loginType == "教师") C#高职计算机导论考试系统设计与实现(16):http://www.751com.cn/jisuanji/lunwen_181.html