用用户登录简单理解三层思想

项目文件列表：

GetUserLoginState.sc

    public class GetUserLoginState
    {
        /// <summary>
        /// 检测用户登录状态
        /// </summary>
        public GetUserLoginState()
        {

        }
        //推荐在此定义类型变量，而不是在方法中new一个新的对象
        private TLoginModel model;


        public UserLoginStateEnum LoginState(string userName, string password, out int ID)
        {
            TLoginDataManager manager = new TLoginDataManager();
            ID = -1;//这里是的编写思想一个亮点
            model = manager.GetUserLoginInfo(userName);
            if (model != null)
            {
                if (model.LockTime == null || DateTime.Compare((DateTime)model.LockTime, DateTime.Now) < 0)
                {
                    if (model.ErrorTimes == null || model.ErrorTimes < 4)//帐户锁定情况判断
                    {
                        MD5Encrypt md5 = new MD5Encrypt();
                        if (model.MD5Password == md5.Encryption(password))
                        {
                            ID = model.ID;
                            return UserLoginStateEnum.LoginSucceed;
                        }
                        else
                        {
                            manager.RaiseErrorTimes(model.ID);
                            return UserLoginStateEnum.PasswordError;
                        }
                    }
                }
                //这里你有疑问吗？
                manager.LockUser(model.ID);
                return UserLoginStateEnum.LoginFailed;
            }
            else
            {
                return UserLoginStateEnum.NoUserName;
            }
        }

        public int ChangePassword(string pwd, int id)
        {
            TLoginDataManager manager = new TLoginDataManager();
            MD5Encrypt md5 = new MD5Encrypt();
            return manager.PasswordChange(md5.Encryption(pwd), id);
        }

        public bool VerifyPassword(string pwd, int id)
        {
            TLoginDataManager manager = new TLoginDataManager();
            MD5Encrypt md5 = new MD5Encrypt();
            return manager.VerifyPassword(md5.Encryption(pwd), id);
        }
    }

MD5Encrypt.cs

    public  class MD5Encrypt
    {
        /// <summary>
        /// 计算字符串 str 的HashValue
        /// </summary>
        /// <param name="str">字符串</param>
        /// <returns>返回 str 的32位HashValue</returns>
        public  string Encryption(string str)
        {
            byte[] strByte = Encoding.UTF8.GetBytes(str);
            MD5 md5 = MD5.Create();
            strByte = md5.ComputeHash(strByte);
            md5.Clear();
            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < strByte.Length; i++)
            {
                sb.Append(strByte[i].ToString("x2"));
            }
            return sb.ToString();
        }
    }

UserLoginStateEnum.cs

    /// <summary>
    /// 表示用户登录状态
    /// </summary>
    public enum UserLoginStateEnum
    {
        NoUserName,
        PasswordError,
        LoginFailed,
        LoginSucceed
    }

SqlHelper.cs

    public class SqlHelper
    {
        /// <summary>
        /// 数据查询帮助类
        /// </summary>
        public SqlHelper()
        {

        }

        private string constr = ConfigurationManager.ConnectionStrings["sql"].ConnectionString;

        /// <summary>
        /// 对连接执行 Transact-SQL 语句并返回受影响的行数。
        /// </summary>
        /// <param name="sql">Transact-SQL 更新语句</param>
        /// <param name="param">参数</param>
        /// <returns>受影响的行数。</returns>
        public int ExecuteNonQuery(string sql, params SqlParameter[] param)
        {
            using (SqlConnection con = new SqlConnection(constr))
            {
                using (SqlCommand cmd = new SqlCommand(sql, con))
                {
                    if (param != null)
                    {
                        cmd.Parameters.AddRange(param);
                    }
                    con.Open();
                    return cmd.ExecuteNonQuery();
                }
            }
        }
        /// <summary>
        /// 将 System.Data.SqlClient.SqlCommand.CommandText 发送到 System.Data.SqlClient.SqlCommand.Connection，并使用
        ///    System.Data.CommandBehavior 值之一生成一个 System.Data.SqlClient.SqlDataReader。
        /// </summary>
        /// <param name="sql">Transact-SQL 查询语句</param>
        /// <param name="param">参数</param>
        /// <returns>System.Data.SqlClient.SqlDataReader 对象。</returns>
        public SqlDataReader ExecuteReader(string sql, params SqlParameter[] param)
        {
            SqlConnection con = new SqlConnection(constr);
            try
            {
                using (SqlCommand cmd = new SqlCommand(sql, con))
                {
                    if (param != null)
                    {
                        cmd.Parameters.AddRange(param);
                    }
                    con.Open();
                    return cmd.ExecuteReader(System.Data.CommandBehavior.CloseConnection);
                }
            }
            catch (Exception)//模拟using(SqlConnection con = new SqlConnection(constr))
            {
                con.Close();
                con.Dispose();
                throw;
            }
        }
        /// <summary>
        /// 执行查询，并返回查询所返回的结果集中第一行的第一列。 忽略其他列或行。
        /// </summary>
        /// <param name="sql">Transact-SQL 查询语句</param>
        /// <param name="param">参数</param>
        /// <returns>结果集中第一行的第一列；如果结果集为空，则为空引用（在 Visual Basic 中为 Nothing）。 返回的最大字符数为 2033 个字符。</returns>
        public object ExecuteScalar(string sql, params SqlParameter[] param)
        {
            using (SqlConnection con = new SqlConnection(constr))
            {
                using (SqlCommand cmd = new SqlCommand(sql, con))
                {
                    if (param != null)
                    {
                        cmd.Parameters.AddRange(param);
                    }
                    con.Open();
                    return cmd.ExecuteScalar();
                }
            }
        }
        /// <summary>
        /// 执行查询，并返回查询所返回的结果集
        /// </summary>
        /// <param name="sql">Transact-SQL 查询语句</param>
        /// <param name="param">参数</param>
        /// <returns>System.Data.DataTable 对象</returns>
        public DataTable ExecuteDataTable(string sql, params SqlParameter[] param)
        {
            DataTable dt = new DataTable();
            using (SqlDataAdapter adapter = new SqlDataAdapter(sql, constr))
            {
                if (param != null)
                {
                    adapter.SelectCommand.Parameters.AddRange(param);
                }
                adapter.Fill(dt);
            }
            return dt;
        }
    }

TLoginDataManager.cs

    public class TLoginDataManager
    {
        /// <summary>
        /// 对Login表的数据管理
        /// </summary>
        public TLoginDataManager()
        {

        }


        public TLoginModel GetUserLoginInfo(string userName)
        {
            SqlHelper sqlhelper = new SqlHelper();
            string sql = "select * from MD5Login where name=@userName";
            using (SqlDataReader reader = sqlhelper.ExecuteReader(sql, new SqlParameter("@userName", userName)))
            {
                if (reader.HasRows)
                {
                    try
                    {
                        TLoginModel userModel = new TLoginModel();
                        while (reader.Read())
                        {
                            userModel.ID = int.Parse(reader[0].ToString());
                            userModel.Name = reader[1].ToString();
                            userModel.MD5Password = reader[2].ToString();
                            //(int)值类型 null 是不可能的：所以要做强制类型转换
                            userModel.ErrorTimes = reader.IsDBNull(3) ? null : (int?)int.Parse(reader[3].ToString());
                            userModel.LockTime = reader.IsDBNull(4) ? null : (DateTime?)DateTime.Parse(reader[4].ToString());
                            userModel.Place = reader[5].ToString();
                        }
                        //读一行可以这样写：读多行时就用List<T>集合。
                        return userModel;
                    }
                    catch (Exception)
                    {
                        throw;
                    }
                }
            }
            //这样做于利于弊，自己权衡吧。
            return null;
        }

        internal void LockUser(int p)
        {
            SqlHelper sqlhelper = new SqlHelper();
            string sql = "update MD5Login set locktime=dateadd(minute,10,getdate()),errortimes=0 where id=@id";
            sqlhelper.ExecuteNonQuery(sql, new SqlParameter("@id", p));
        }

        internal void RaiseErrorTimes(int p)
        {
            SqlHelper sqlhelper = new SqlHelper();
            string sql = "update MD5Login set errortimes=errortimes+1 where id=@id";
            sqlhelper.ExecuteNonQuery(sql, new SqlParameter("@id", p));
        }

        public int PasswordChange(string pwd, int id)
        {
            SqlHelper sqlhelper = new SqlHelper();
            string sql = "update MD5Login set MD5pwd=@pwd where id=@id";
            return sqlhelper.ExecuteNonQuery(sql, new SqlParameter("@pwd", pwd), new SqlParameter("@id", id));
        }


        internal bool VerifyPassword(string p, int id)
        {
            SqlHelper sqlhelper = new SqlHelper();
            string sql = "select * from MD5Login where id=@id and MD5pwd=@pwd";
            return sqlhelper.ExecuteReader(sql, new SqlParameter("@id", id), new SqlParameter("@pwd", p)).HasRows;
        }
    }

TLoginModel.cs

 public class TLoginModel
    {
        /// <summary>
        /// Login表数据模板类
        /// </summary>
        public TLoginModel()
        {

        }
        /// <summary>
        /// 用户id
        /// </summary>
        public int ID { get; set; }
        /// <summary>
        /// 用户名称
        /// </summary>
        public string Name { get; set; }

        //用不用储存密码？
        /// <summary>
        /// 用户密码的MD5值
        /// </summary>
        public string MD5Password { get; set; }

        /// <summary>
        /// 登录错误次数
        /// int? 表示int的可空类型（Nullable)
        /// </summary>
        public int? ErrorTimes { get; set; }

        /// <summary>
        /// 帐户锁定时间
        /// DateTime? 表示DateTime的可空类型（Nullable）
        /// </summary>
        public DateTime? LockTime { get; set; }
        /// <summary>
        /// 登录地点
        /// </summary>
        public string Place { get; set; }
        /// string? :错误的！！值类型 are nullable not
    }

UserCurrentID.cs

    public static class UserCurrentID
    {
        public static int ID { get; set; }
    }

frmLogin类

    public partial class frmLogin : Form
    {
        public frmLogin()
        {
            InitializeComponent();
        }

        private UserLoginStateEnum state;

        private void btnLogin_Click(object sender, EventArgs e)
        {
            GetUserLoginState login = new GetUserLoginState();
            string name = txtUserName.Text.Trim();
            string password = txtPassword.Text.Trim();
            //在这里有UI的BLL，当然也可以写在BLL中
            //判断输入框不能为空的情况。
            //属性、索引器或动态成员访问不得作为 out 或 ref 参数传递    
            //state = login.LoginState(name, password, out  UserCurrentID.ID);
            int ID;
            state = login.LoginState(name, password, out ID);
            if (state == UserLoginStateEnum.LoginSucceed)
            {
                UserCurrentID.ID = ID;
                MessageBox.Show("登录成功");
                this.btnPasswordChange.Enabled = true;
            }
            else if (state == UserLoginStateEnum.NoUserName)
            {
                MessageBox.Show("用户不存在");
            }
            else if (state == UserLoginStateEnum.PasswordError)
            {
                MessageBox.Show("密码错误");
            }
            else if (state == UserLoginStateEnum.LoginFailed)
            {
                MessageBox.Show("错误次数过多，锁定10分钟，稍后再试。");
            }
        }

        private void btnPasswordChange_Click(object sender, EventArgs e)
        {
            PasswordChange changePwd = new PasswordChange();

            changePwd.Show();
        }
    }

PasswordChange类

    public partial class PasswordChange : Form
    {
        public PasswordChange()
        {
            InitializeComponent();
        }

        private void btnCancel_Click(object sender, EventArgs e)
        {
            this.Dispose();
        }

        private void btnOK_Click(object sender, EventArgs e)
        {
            GetUserLoginState state = new GetUserLoginState();
            //这里便是UI层的BLL，
            //当然也可以在BLL中设计（和登录状态类似的设计）
            if (state.VerifyPassword(txtOriginalPassword.Text.Trim(), UserCurrentID.ID))
            {
                if (txtNewPassword.Text.Trim() == txtVerifyNewPassword.Text.Trim())
                {
                    state.ChangePassword(txtVerifyNewPassword.Text.Trim(), UserCurrentID.ID);
                    MessageBox.Show("密码修改成功");
                }
                else
                    MessageBox.Show("两次密码不一致");
            }
            else
                MessageBox.Show("原密码错误");
        }
    }

项目文件:http://pan.baidu.com/s/1sjpUCCP