第一次尝试三层架构<实现简单的增、删、查、改>

三层架构：UI（界面，User Interfa）、BLL（业务逻辑层）以及DAL（数据访问层）。三层之间通过Model实现数据的传递。在使用中牢记，三层之间的访问权限;UI→BLL→DAL。

采用三层架构的优点：高可拓展性、可维护性高，不足之处：工作量大、系统比较复杂(感觉最好是精通设计思想,如设计模式)、效率比较低。

项目的结构图：

建立相应的文件夹

首先配置应用程序配置文件 App.config

配置如下：

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <connectionStrings>
    <add name="cons" connectionString="server=(local);user id=sa; pwd=********;database=GUbase"/>//连接字符串
  </connectionStrings>
</configuration>

 

封装的数据库操作SQlHelper.cs

sing System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Configuration;
using System.Data.SqlClient;
using System.Data;

namespace 三层架构.DAL
{
    class SQlHelper
    {
        private static readonly string cons = ConfigurationManager.ConnectionStrings["cons"].ConnectionString;//读取配置文件的连接字符串

        #region ExecuteNoQuery//用于执行非查询语句
        /// <summary>
        /// ExecuteNoQuery
        /// </summary>
        /// <param name="sql">sql语句</param>
        /// <param name="Parameters">参数</param>
        /// <returns></returns>
        public static int ExecuteNoQuery(string sql, params SqlParameter[] Parameters)
        {
            using (SqlConnection con = new SqlConnection(cons))
            {
                con.Open();
                using (SqlCommand cmd = con.CreateCommand())
                {
                    cmd.CommandText = sql;
                    cmd.Parameters.AddRange(Parameters);
                    return cmd.ExecuteNonQuery();
                }
            }

        } 
        #endregion
        #region  ExecuteScalar
        /// <summary>
        ///  ExecuteScalar//查询相关
        /// </summary>
        /// <param name="sql">sql语句</param>
        /// <param name="Parameters">参数/param>
        /// <returns></returns>
        public static object ExecuteScalar(string sql, params SqlParameter[] Parameters)
        {
            using (SqlConnection con = new SqlConnection(cons))
            {
                con.Open();
                using (SqlCommand cmd = con.CreateCommand())
                {
                    cmd.CommandText = sql;
                    cmd.Parameters.AddRange(Parameters);
                    return cmd.ExecuteScalar();
                }
            }
        }  
        #endregion
        #region ExecuteDataTable
        /// <summary>
        /// ExecuteDataTable//查询获取相关字段的值
        /// </summary>
        /// <param name="sql">sql语句</param>
        /// <param name="Parameters">参数/param>
        /// <returns></returns>
        public static DataTable ExecuteDataTable(string sql, params SqlParameter[] Parameters)
        {
            using (SqlConnection con = new SqlConnection(cons))
            {
                con.Open();
                using (SqlCommand cmd = con.CreateCommand())
                {
                    cmd.CommandText = sql;
                    cmd.Parameters.AddRange(Parameters);
                    DataTable table = new DataTable();
                    SqlDataAdapter adapter = new SqlDataAdapter(cmd);
                    adapter.Fill(table);
                    return table;
                }
            }
        } 
        #endregion
    }
}

 

Model文件下的Person.cs 封装z字段相关，用于在三层之间数据的传递

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

namespace 三层架构.Model
{
    class Person
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public int Age { get; set; }
    }
}

DAl下的PersonDAL.cs用于和数据库执行各种操作的SQL语句和方法

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using 三层架构.Model;
using System.Data.SqlClient;
using System.Data;

namespace 三层架构.DAL
{
    class PersonDAL
    {
        #region 新增
        /// <summary>
        /// 新增
        /// </summary>
        /// <param name="model">对象</param>
        /// <returns></returns>
        public int AddNew(Person model)//把要插入数据的模型传递给AddNew()
        {
            object obj = SQlHelper.ExecuteScalar("insert into  T_Person(Name,Age) values(@Name,@Age);select @@identity", new SqlParameter("Name", model.Name), new SqlParameter("Age", model.Age));//select @@identity执行插入后返回主键值
            return Convert.ToInt32(obj);
        } 
        #endregion

        #region 删除
        public int Delete(int id)
        {
            return SQlHelper.ExecuteNoQuery("delete from T_Person where Id=@Id", new SqlParameter("Id", id));
        } 
        #endregion
        #region 更新
        public int Update(Person model)
        {
            return SQlHelper.ExecuteNoQuery("update T_Person set Name=@Name, Age=@Age where Id=@Id", new SqlParameter("Id", model.Id), new SqlParameter("Name", model.Name), new SqlParameter("Age", model.Age));
        } 
        #endregion
        #region 查询
        public Person GetData(int id)
        {
            DataTable dt = SQlHelper.ExecuteDataTable("select * from T_Person where Id=@Id", new SqlParameter("Id", id));
            if (dt.Rows.Count < 0)
            {
                return null;
            }
            else if (dt.Rows.Count == 1)
            {
                DataRow row = dt.Rows[0];
                Person model = new Person();
                model.Id = Convert.ToInt32(row["Id"]);
                model.Name = Convert.ToString(row["Name"]);
                model.Age = Convert.ToInt32(row["Age"]);
                return model;
            }
            else
            {
                throw new Exception("数据出错，多条数据");
            }
        } 
        #endregion
        public IEnumerable<Person> GetAll()//IEnumerable<Person>使用该接口实现只读性
        {
            DataTable dt = SQlHelper.ExecuteDataTable("select * from T_Person");
            List<Person> list = new List<Person>();
            foreach (DataRow row in dt.Rows)
            {
                Person model = new Person();
                model.Id = Convert.ToInt32(row["Id"]);
                model.Name= Convert.ToString(row["Name"]);
                model.Age = Convert.ToInt32(row["Age"]);
                list.Add(model);
            }
            return list;
        }
    }
}

BLL下的PersonBLL.cs用于执行和数据库交互前业务逻辑的判断处理

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using 三层架构.Model;
using 三层架构.DAL;
using System.Data.SqlClient;

namespace 三层架构.BLL
{
    class PersonBLL
    {
        #region 新增
      
        public int AddNew(Person model)//把要插入数据的模型传递给AddNew()
        {
            return new PersonDAL().AddNew(model);
        }
        #endregion

        #region 删除
        public int Delete(int id)
        {
            return new PersonDAL().Delete(id);
        }
        #endregion
        #region 更新
        public int Update(Person model)
        {
            //BLL进行逻辑判断，DAL只进行数据库的操作！，这就是BLL和DAL的区别
            if (model.Age <10)
            {
                throw new Exception("年龄非法！！");
            }
            return new PersonDAL().Update(model);
        }
        #endregion
        #region 查询
        public Person GetData(int id)
        {
          return  new PersonDAL().GetData(id);
        }
        #endregion
        public IEnumerable<Person> GetAll()//IEnumerable<Person>使用该接口实现只读性
        {
            return new PersonDAL().GetAll();
        }
    }
}

UI界面

 采用三层架构用户界面变得相当简洁

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using 三层架构.Model;
using 三层架构.DAL;
using 三层架构.BLL;

namespace 三层架构
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            Person p1 = new Person();
            p1.Age = 20;
            p1.Name = "小文";
           int id= new PersonBLL().AddNew(p1);
           MessageBox.Show(id.ToString());
        }

        private void button2_Click(object sender, EventArgs e)
        {
            int Id = 3;
            int count = new PersonBLL().Delete(Id);
            MessageBox.Show("删除成功！！");
        }

        private void button3_Click(object sender, EventArgs e)
        {
            Person p = new Person();
            p.Id = 1;
            p.Name = "想你";
            p.Age = 21;
            new PersonBLL().Update(p);
            MessageBox.Show("更新成功！！");
        }

        private void button4_Click(object sender, EventArgs e)
        {
            int id = 1;
           Person p= new PersonBLL().GetData(id);
           int Id = p.Id;
           int Age = p.Age;
           MessageBox.Show(Id.ToString());
           MessageBox.Show(p.Name);
           MessageBox.Show(Age.ToString());
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            dataGridView1.DataSource = new PersonBLL().GetAll();
        }
    }
}

 <下篇博客主要是根据本篇的代码格式，完成自己的三层架构的代码生成器,居然现在市面上有很多的代码生成器，但有的时候还是更加喜欢自己的风格，今天写了一些，估计过几天就可以完成，到时候发到博客上，揭秘代码生成器的原理>