三层学习

public class DBHelper
    {
        private static SqlConnection conn = new SqlConnection("server=.;database=HR;uid=sa;pwd=;");
        /// <summary>
        /// 封装SqlCommand对象的ExecuteNonQuery方法
        /// </summary>
        /// <param name="strsql">传入以insert|update|delete打头的SQL语句</param>
        /// <returns>返回执行影响的行数</returns>
        public static int ExecuteNonQuery(string strsql)
        {
            SqlCommand comm = new SqlCommand(strsql, conn);
            try
            {
                conn.Open();
                return comm.ExecuteNonQuery();
            }
            catch
            {
                throw;
            }
            finally
            {
                conn.Close();
            }
        }
        /// <summary>
        /// 返回数据集DataSet
        /// </summary>
        /// <param name="strsql">以Select打头的SQL语句</param>
        /// <returns>返回DataSet对象</returns>
        public static DataSet GetDataSet(string strsql)
        {
            SqlDataAdapter da = new SqlDataAdapter(strsql, conn);
            DataSet ds = new DataSet();
            try
            {
                da.Fill(ds);
                return ds;
            }
            catch
            {
                throw;
            }
        }
        /// <summary>
        /// 返回DataTable对象
        /// </summary>
        /// <param name="strsql">以Select打头的SQL语句</param>
        /// <returns>返回DataTable对象</returns>
        public static DataTable GetDataTable(string strsql)
        {
            DataSet ds = GetDataSet(strsql);
            if (ds != null)
            {
                return ds.Tables[0];
            }
            else
                return null;
        }
        /// <summary>
        /// 返回首行首列的单元格的值(封装Command对象的ExecuteScalar方法)
        /// </summary>
        /// <param name="strsql">Select打头的SQL语句</param>
        /// <returns>返回的是Object</returns>
        public static object GetScalar(string strsql)
        {
            SqlCommand comm = new SqlCommand(strsql, conn);
            try
            {
                conn.Open();
                return comm.ExecuteScalar();
            }
            catch (Exception)
            {
                throw;
            }
            finally
            {
                conn.Close();
            }
        }
    }

using System;
using System.Collections.Generic;
using System.Text;
using System.Data;
using TheOneHR.Models;

namespace TheOneHR.DAL
{
    public class UserInfoService
    {
        private static IList<UserInfo> GetUsersBySQL(string strsql)//内部方法  泛型集合
        {
            IList<UserInfo> users = new List<UserInfo>();
            DataTable dt = DBHelper.GetDataTable(strsql);
            if (dt != null)
            {
                for (int i = 0; i < dt.Rows.Count; i++)
                {
                    UserInfo user = new UserInfo();
                    user.Id =int.Parse( dt.Rows[i]["Id"].ToString());
                    user.User_name = dt.Rows[i]["Users_name"].ToString();
                    user.User_password = dt.Rows[i]["Users_password"].ToString();
                    //注意外键列的处理
                    user.Sys_role = Sys_roleService.GetSys_roleById(int.Parse(dt.Rows[i]["Roleno"].ToString()));
                    users.Add(user);
                }
 
            }
            return users;
        }
        /// <summary>
        /// 得到所有用户列表
        /// </summary>
        /// <returns></returns>
        public static IList<UserInfo> GetAllUserInfos()
        {
            string strsql = "select * from UserInfo";
            return GetUsersBySQL(strsql);

        }
        /// <summary>
        /// 根据用户ID得用户实体
        /// </summary>
        /// <param name="id"></param>
        /// <returns></returns>
        public static UserInfo GetUserById(int id)
        {
            string strsql = "select * from UserInfo where Id=" + id.ToString();
            try
            {
                return GetUsersBySQL(strsql)[0];
            }
            catch
            {
                return null;
            }
        }
        /// <summary>
        /// 添加一个用户
        /// </summary>
        /// <param name="user"></param>
        /// <returns></returns>
        public static int AddUser(UserInfo user)
        {
            string strsql = string.Format("INSERT INTO [UserInfo] ([Users_name],[Users_password] ,[Roleno])VALUES('{0}','{1}',{2})", user.User_name, user.User_password, user.Sys_role.Id);
            return DBHelper.ExecuteNonQuery(strsql);
        }
        /// <summary>
        /// 修改一个用户信息
        /// </summary>
        /// <param name="user"></param>
        /// <returns></returns>
        public static int ModifyUser(UserInfo user)
        {
            string strsql = string.Format("UPDATE [UserInfo] SET [Users_name] = '{0}',[Users_password] = '{1}' ,[Roleno] = {2} WHERE Id={3}", user.User_name, user.User_password, user.Sys_role.Id, user.Id);
            return DBHelper.ExecuteNonQuery(strsql);
        }
        /// <summary>
        /// 删除一个用户
        /// </summary>
        /// <param name="id"></param>
        /// <returns></returns>
        public static int DelUser(int id)
        {
            string strsql = "delete from UserInfo where Id=" + id.ToString();
            return DBHelper.ExecuteNonQuery(strsql);
        }
        /// <summary>
        /// 根据帐号得用户实体
        /// </summary>
        /// <param name="loginId">登录帐号</param>
        /// <returns></returns>
        public static UserInfo GetUserByLoginId(string loginId)
        {
            string strsql = string.Format("select * from UserInfo where Users_name='{0}'", loginId);
            try
            {
                return GetUsersBySQL(strsql)[0];
            }
            catch
            {
                return null;
            }
 
        }

    }
}

using System;
using System.Collections.Generic;
using System.Text;
using TheOneHR.Models;
using TheOneHR.DAL;


namespace TheOneHR.BLL
{
    public class UserInfoManager
    {
        /// <summary>
        /// 得到所有用户列表
        /// </summary>
        /// <returns></returns>
        public static IList<UserInfo> GetAllUserInfos()
        {
            return TheOneHR.DAL.UserInfoService.GetAllUserInfos();//使用数据访问层的方法
        }
        /// <summary>
        /// 根据用户ID得用户实体
        /// </summary>
        /// <param name="id"></param>
        /// <returns></returns>
        public static UserInfo GetUserById(int id)
        {
            return TheOneHR.DAL.UserInfoService.GetUserById(id);
        }
        /// <summary>
        /// 添加一个用户
        /// </summary>
        /// <param name="user"></param>
        /// <returns></returns>
        public static bool AddUser(UserInfo user)//添加成功或失败
        {
            return TheOneHR.DAL.UserInfoService.AddUser(user)>0; //大于0则返回true  等于0则返回false
        }
        /// <summary>
        /// 修改一个用户信息
        /// </summary>
        /// <param name="user"></param>
        /// <returns></returns>
        public static bool ModifyUser(UserInfo user)
        {
            return TheOneHR.DAL.UserInfoService.ModifyUser(user)>0;
        }
        /// <summary>
        /// 删除一个用户
        /// </summary>
        /// <param name="id"></param>
        /// <returns></returns>
        public static bool DelUser(int id)
        {
            return TheOneHR.DAL.UserInfoService.DelUser(id)>0;
        }

    }
}