简单工厂实现支持不同数据库

业务描述：通过简单工厂设计模式实现对不同数据库的支持（如：Ms Sqlserver,MySql）

思路：

解决方案下包括以下项目

1. 项目StudyEntity(定义对象的结构)、接口
2. 项目StudyDal(MySqlStudyDal) 数据层（两个项目）
3. 项目StudyBll  业务逻辑层
4. Web层

引用关系：

数据层引用StudyEntity

业务逻辑层引用StudyEntity、数据层

Web层引用StudyEntity、业务逻辑层

StudyEntity层代码 User.cs：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace StudyEntity
{
    public class User
    {
        public string Staffno
        {
            get;
            set;
        }

        public string UserName
        {
            get;
            set;
        }

    }
}

StudyEntity层代码 IUser.cs：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace StudyEntity
{
    public interface IUser
    {
        User GetItem(string userStaffno);
        User Save(User user);
    }
}

数据层StudyDal [MSSqlServer 数据库]

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using StudyEntity;

namespace StudyDal
{
    public class UserDal:IUser
    {
        #region IUser 成员

        public User GetItem(string userStaffno)
        {
            User user = new User();
            user.Staffno = "200718";
            user.UserName = "Snow";
            return user;
        }

        public User Save(User user)
        {
            throw new NotImplementedException();
            
        }

        #endregion
    }
}

数据层 MySqlDal [My Sql 数据库]

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using StudyEntity;

namespace MySqlDal
{
    public class MySqlUserDal:IUser
    {
        #region IUser 成员

        public User GetItem(string userStaffno)
        {
            User user = new User();
            user.Staffno = "200500";
            user.UserName = "MySql";
            return user;
        }

        public User Save(User user)
        {
            throw new NotImplementedException();
        }

        #endregion
    }
}

业务逻辑层StudyBLL 之 UserBll

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using StudyEntity;
using StudyDal;

namespace StudyBLL
{
    public class UserBll
    {
        /// <summary>
        /// 通过工号获取员工
        /// </summary>
        /// <param name="staffNumber"></param>
        /// <returns></returns>
        public User GetItem(string staffNumber)
        {
            UserDal userDal = new UserDal();

            return userDal.GetItem(staffNumber);
        }
    }
}

业务逻辑层StudyBLL 之工厂类（Factory.cs）

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using StudyEntity;
using StudyDal;
using MySqlDal;

namespace StudyBLL
{
    public class Factoy
    {
        public static IUser CreateUserInstance(string dbType)
        {
            IUser user;

            switch (dbType)
            { 
                case "1":
                    user = new UserDal();
                    break;
                case "2":
                    user = new MySqlUserDal();
                    break;
                default:
                    user = null;
                    break;
            }
            return user;
        }
    }
}

Web层调用：传递的参数1 或 2 可通过webConfig文件配置

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using StudyBLL;
using StudyEntity;


namespace Study2018
{
    /// <summary>
    /// 程序支持不同数据库的代码写法
    /// </summary>
    public partial class TestGetUser : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        protected void btnGetUser_Click(object sender, EventArgs e)
        {
            User user = Factoy.CreateUserInstance("1").GetItem("xxx");
            Response.Write(user.Staffno + user.UserName); 

        }

        protected void btnGetMySqlUser_Click(object sender, EventArgs e)
        {
            User user = Factoy.CreateUserInstance("2").GetItem("xxx");
            Response.Write(user.Staffno + user.UserName); 
        }
    }
}