C#&SQL Server基于三层架构实现增删改查

vlambda
2021-06-17

C#&SQL Server基于三层架构实现增删改查

C # SQL Server implement CRUD-based three-tier architecture

先来看看C#和SQL Server的整个框架

SQL Server

这是本次使用到数据库的一些信息

服务器名称：DESKTOP-D258CHD\WINCC

登录用户：sa 密码：123

数据库：Architecture_demo 表名：Student

C#&SQL Server基于三层架构实现增删改查

清楚了框架那么现在开始编写C#部分的程序

1_首先创建以下四个项目

BLL、DAL、Model为".dll类库"项目，UI为"Windows窗体应用程序"项目

C#&SQL Server基于三层架构实现增删改查

2_Model实体模型搭建

创建Students类，且Students要为public

C#中的Students类与数据库中的Student的表，是多了一个“s”的，用于区分

这里的属性要与数据库中的Student表要一样

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;
namespace Model{ public class Students { public int student_ID { get; set; } public string name { get; set; } public int age { get; set; } public string gender { get; set; } }}

C#&SQL Server基于三层架构实现增删改查

3_DAL数据访问层

首先在UI项目里的App.config文件中添加一段代码，在数据库服务器名称和密码发生改变时，不用修改程序代码，只需要修改App.config文件中这段代码既可

Server：数据库服务器的名称 DataBase：数据库名称

Uid：用户名 Pwd：密码

C#&SQL Server基于三层架构实现增删改查

 <connectionStrings> <add name="connString" connectionString="Server=DESKTOP-D258CHD\WINCC;DataBase=Architecture_demo;Uid=sa;Pwd=123" /> </connectionStrings>

然后返回到DAL项目，在DAL项目引用里添加System.Configuration，用于读取UI项目的App.config文件

C#&SQL Server基于三层架构实现增删改查

在DAL项目里创建SQLHelper类，SQLHelper要为public，同时引入System.Data、System.Data.SqlClient、System.Configuration

System.Data：提供对数据的操作

System.Data.SqlClient：提供对数据库的操作

System.Configuration：提供对App.config的操作

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;
using System.Data;using System.Data.SqlClient;using System.Configuration;
namespace DAL{ public class SQLHelper {
 }}

开始编写数据访问层代码

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;
using System.Data;using System.Data.SqlClient;using System.Configuration;
namespace DAL{ public class SQLHelper { private static readonly string connString = ConfigurationManager.ConnectionStrings["connString"].ToString();
 /// <summary> /// 对数据库进行增删改 /// </summary> /// <param name="sql">要查询的SQL语句</param> /// <returns>返回受影响的行数</returns> public static int Update(string sql) { //与数据库连接的字符串 SqlConnection conn = new SqlConnection(connString); //SQL语句 SqlCommand cmd = new SqlCommand(sql, conn); try { //与数据库建立连接 conn.Open(); return cmd.ExecuteNonQuery(); } catch (Exception ex) {
 throw ex; } finally { //断开与数据库的连接 conn.Close(); } }

 /// <summary> /// 执行单一结果查询 /// </summary> /// <param name="sql">要查询的SQL语句</param> /// <returns>返回单一的查询结果</returns> public static object GetSingleResult(string sql) { SqlConnection conn = new SqlConnection(connString); SqlCommand cmd = new SqlCommand(sql, conn); try { conn.Open(); return cmd.ExecuteScalar(); } catch (Exception ex) {
 throw ex; } finally { conn.Close(); } }
 /// <summary> /// 执行一个结果集的查询 /// </summary> /// <param name="sql">要查询的SQL语句</param> /// <returns>返回一个SqlDataReader对象</returns> public static SqlDataReader GetReader(string sql) { SqlConnection conn = new SqlConnection(connString); SqlCommand cmd = new SqlCommand(sql, conn); try { conn.Open(); SqlDataReader objReader = cmd.ExecuteReader(CommandBehavior.CloseConnection); return objReader; } catch (Exception ex) {
 throw ex; } }

 }}

4_BLL业务逻辑层

在BLL里创建StudentService类，StudentService要为public

引入DAL、Model

C#&SQL Server基于三层架构实现增删改查

接着在StudentService类的代码里引入

System.Data、System.Data.SqlClient

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;
using System.Data;using System.Data.SqlClient;using DAL;using Model;
namespace BLL{ public class StudentService {
 }}

开始编写业务逻辑层代码

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;
using System.Data;using System.Data.SqlClient;using DAL;using Model;
namespace BLL{ public class StudentService {
 /// <summary> /// 增加一条数据 /// </summary> /// <param name="objStudent"></param> /// <returns></returns> public int AddStudent(Students objStudent) { //【1】编写sql语句 StringBuilder sqlBuilder = new StringBuilder("insert into Student "); sqlBuilder.Append(" (name,age,gender) "); sqlBuilder.Append(" values('{0}',{1},'{2}');select @@identity "); //【2】解析对象 string sql = string.Format(sqlBuilder.ToString(), objStudent.name,objStudent.age,objStudent.gender);
 //【3】提交SQL语句 try { return Convert.ToInt32(SQLHelper.GetSingleResult(sql));//执行sql语句，返回学号 } catch (Exception ex) { throw new Exception("添加学员时数据访问异常：" + ex.Message); } }
 /// <summary> /// 删除一条数据 /// </summary> /// <param name="studentId"></param> /// <returns></returns> public int DeleteStudent(string studentId) { string sql = "delete from Student where Student_ID=" + studentId; try { return SQLHelper.Update(sql); } catch (SqlException ex) { //547是数据库返回的消息，返回改该消息表示不能被删除 if (ex.Number == 547) { throw new Exception("该学号被其他实体引用，不能直接删除该学员对象！"); } else { throw new Exception("删除学员对象发生数据异常！" + ex.Message); } } catch (Exception ex) { throw ex; } }

 /// <summary> /// 修改学生信息 /// </summary> /// <param name="objStudent"></param> /// <returns></returns> public int ModifyStudent(Students objStudent) { StringBuilder sqlBuilder = new StringBuilder(); sqlBuilder.Append("update Student set name='{0}',age={1},gender='{2}' "); string sql = string.Format(sqlBuilder.ToString(), objStudent.name,objStudent.age,objStudent.gender); try { return SQLHelper.Update(sql); } catch (Exception ex) { throw new Exception("修改学员信息是数据访问发生异常：" + ex.Message); } }
 /// <summary> /// 根据学号查询学生 /// </summary> /// <param name="studentId"></param> /// <returns></returns> public Students GetStudentById(string studentId) { string sql = "select Student_ID,name,age,gender from Student "; sql += " where Student_ID=" + studentId; SqlDataReader objReader = SQLHelper.GetReader(sql); Students objStudent = null; if (objReader.Read()) { objStudent = new Students() { student_ID=Convert.ToInt32(objReader["student_ID"]), name=objReader["name"].ToString(), age = Convert.ToInt32(objReader["age"]), gender=objReader["gender"].ToString() }; } objReader.Close(); return objStudent; }
 }}

5_UI表现层

在工具箱找到TabControl，拖动到窗口

C#&SQL Server基于三层架构实现增删改查

增加两个页面，第一个为“增”，第二个为“删、改、查”，并且修改界面

“增”界面

这里说明一下因为学号在数据库里面是主键，是不能更改的，但是在添加其他数据的时候，学号是会自增数据的，每一条数据+1，这个每次增加的数可以在数据库里面修改的 C#&SQL Server基于三层架构实现增删改查

“删、改、查”界面

C#&SQL Server基于三层架构实现增删改查

引入DAL、BLL、Model

C#&SQL Server基于三层架构实现增删改查

using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Drawing;using System.Linq;using System.Text;using System.Threading.Tasks;using System.Windows.Forms;
using DAL;using BLL;using Model;
namespace UI{ public partial class Form1 : Form { public Form1() { InitializeComponent(); }
 }}

开始编写UI表现层代码

“增”界面代码

using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Drawing;using System.Linq;using System.Text;using System.Threading.Tasks;using System.Windows.Forms;
using DAL;using BLL;using Model;
namespace UI{ public partial class Form1 : Form { private StudentService objStudentService = new StudentService(); List<Students> stuList = new List<Students>();//用来临时保存学员对象
 public Form1() { InitializeComponent(); }

 /// <summary> /// 添加按钮 /// </summary> /// <param name="sender"></param> /// <param name="e"></param> private void btn_Add_Click(object sender, EventArgs e) { //封装学生对象 Students ojbStudent = new Students() { name = this.txt_Z_name.Text.Trim(), age = Convert.ToInt32(this.txt_Z_age.Text.Trim()), gender = this.rdoMale.Checked ? "男" : "女" };
 //调用后台数据访问方法 int studentId = objStudentService.AddStudent(ojbStudent);
 try { //同步显示添加的学员 ojbStudent.student_ID = studentId; this.stuList.Add(ojbStudent); this.dgvStudentList.DataSource = null; this.dgvStudentList.DataSource = this.stuList;
 //询问是否继续添加 DialogResult result = MessageBox.Show("新学员添加成功！是否继续添加？", "提示信息", MessageBoxButtons.YesNo, MessageBoxIcon.Question);
 if (result == DialogResult.Yes) { //清空用户输入的信息 foreach (Control item in this.gbstuinfo.Controls) { if (item is TextBox) { item.Text = ""; } else if (item is RadioButton) { ((RadioButton)item).Checked = false; } } }
 } catch (Exception ex) { MessageBox.Show("添加学员出现数据访问异常" + ex.Message); }


 }
 }}

C#&SQL Server基于三层架构实现增删改查

“删、改、查”界面代码，和“增”界面的一起，这里就是UI全部的代码

using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Drawing;using System.Linq;using System.Text;using System.Threading.Tasks;using System.Windows.Forms;
using DAL;using BLL;using Model;
namespace UI{ public partial class Form1 : Form { private StudentService objStudentService = new StudentService(); List<Students> stuList = new List<Students>();//用来临时保存学员对象
 public Form1() { InitializeComponent(); }

 /// <summary> /// 添加按钮 /// </summary> /// <param name="sender"></param> /// <param name="e"></param> private void btn_Add_Click(object sender, EventArgs e) { //封装学生对象 Students ojbStudent = new Students() { name = this.txt_Z_name.Text.Trim(), age = Convert.ToInt32(this.txt_Z_age.Text.Trim()), gender = this.rdoMale.Checked ? "男" : "女" };
 //调用后台数据访问方法 int studentId = objStudentService.AddStudent(ojbStudent);
 try { //同步显示添加的学员 ojbStudent.student_ID = studentId; this.stuList.Add(ojbStudent); this.dgvStudentList.DataSource = null; this.dgvStudentList.DataSource = this.stuList;
 //询问是否继续添加 DialogResult result = MessageBox.Show("新学员添加成功！是否继续添加？", "提示信息", MessageBoxButtons.YesNo, MessageBoxIcon.Question);
 if (result == DialogResult.Yes) { //清空用户输入的信息 foreach (Control item in this.gbstuinfo.Controls) { if (item is TextBox) { item.Text = ""; } else if (item is RadioButton) { ((RadioButton)item).Checked = false; } } }
 } catch (Exception ex) { MessageBox.Show("添加学员出现数据访问异常" + ex.Message); }


 }
 /// <summary> /// 查询按钮 /// </summary> /// <param name="sender"></param> /// <param name="e"></param> private void btn_Inquire_Click(object sender, EventArgs e) { if (this.txt_S_StudentId.Text.Length == 0) { MessageBox.Show("请输入学号！", "查询提示！"); return; } Students objStudent = objStudentService.GetStudentById(this.txt_S_StudentId.Text.Trim()); this.stuList.Add(objStudent); this.dgvStudentList2.DataSource = null; this.dgvStudentList2.DataSource = this.stuList; }

 /// <summary> /// 修改按钮 /// </summary> /// <param name="sender"></param> /// <param name="e"></param> private void btn_Edit_Click(object sender, EventArgs e) { if (txt_S_Id.Text == ""||txt_S_name.Text==""||txt_S_age.Text==""||rdo_S_Male.Checked==false&&rdo_S_Female.Checked==false) { MessageBox.Show("数据不完整", "提示！"); return; } //封装学员对象 Students objStudent = new Students() { student_ID=Convert.ToInt32(this.txt_S_Id.Text.Trim()), name = this.txt_S_name.Text.Trim(), age=Convert.ToInt32(this.txt_S_age.Text.Trim()), gender=this.rdoMale.Checked ? "男" : "女" };
 try { if (objStudentService.ModifyStudent(objStudent) == 1) { MessageBox.Show("学员信息修改成功！", "提示信息"); } } catch (Exception ex) { MessageBox.Show(ex.Message, "提示信息"); }

 }
 private void dgvStudentList2_CellClick(object sender, DataGridViewCellEventArgs e) { txt_S_Id.Text= this.dgvStudentList2.CurrentRow.Cells["Student_ID"].Value.ToString(); txt_S_name.Text = this.dgvStudentList2.CurrentRow.Cells["name"].Value.ToString(); txt_S_age.Text = this.dgvStudentList2.CurrentRow.Cells["age"].Value.ToString(); if (this.dgvStudentList2.CurrentRow.Cells["gender"].Value.ToString() == "男") { rdo_S_Male.Checked = true; } else { rdo_S_Female.Checked = true; } }
 private void btn_Delete_Click(object sender, EventArgs e) {
 if (this.dgvStudentList2.RowCount == 0) { MessageBox.Show("没有任何需要删除的学员！", "提示信息"); return; } if (this.dgvStudentList2.CurrentRow == null) { MessageBox.Show("请先选中要删除的学员！", "提示信息"); return; }
 //删除前的确认 DialogResult result = MessageBox.Show("确认删除吗！", "提示信息", MessageBoxButtons.OKCancel, MessageBoxIcon.Question); if (result == DialogResult.Cancel) return;
 //获取学号 string studentId = this.dgvStudentList2.CurrentRow.Cells["Student_ID"].Value.ToString(); try { objStudentService.DeleteStudent(studentId); dgvStudentList2.DataSource = null; } catch (Exception ex) {
 MessageBox.Show(ex.Message, "提示信息"); }

 } }}