对三层的基本知识已经有了一定的了解和掌握,但是要想真正去灵活运用它还需要我们去实践,只有经过亲自动手操作实现后才能理解得更加透彻。
首先我们需要建一张数据表,以我的为例,建一张Users表,添加UserName、Password、Email等字段。
然后就开始在VS上进行操作,先建一些基本的项目,如下表:
实体类是贯穿于三层之间,进行数据传递:
Public Class UserInfo Public ID As Integer Public UserName As String Public Password As String Public Email As String Property UID As Integer Get Return ID End Get Set(value As Integer) ID = value End Set End Property Property UUserName As String Get Return UserName End Get Set(value As String) UserName = value End Set End Property Property UPassword As String Get Return Password End Get Set(value As String) Password = value End Set End Property Property UEmail As String Get Return Email End Get Set(value As String) Email = value End Set End Property End Class
DAL层是对数据库进行操作:
Imports System Imports System.Collections.Generic Imports System.Linq Imports System.Text Imports System.Data Imports System.Data.SqlClient Imports Add.Model Public Class UserDAO Public Function ConnectString() As String '连接数据库 ConnectString = "server=.;UID=sa;PWD=123456;database=Login" End Function Public Function AddUser(ByVal userinfo As UserInfo) As Boolean Dim con As SqlClient.SqlConnection Dim cmd As SqlClient.SqlCommand Dim intResult As Integer con = New SqlClient.SqlConnection(ConnectString()) cmd = con.CreateCommand() cmd.CommandText = "insert into Users(UserName,Password,Email) values('" & userinfo.UserName & "','" & userinfo.Password & "','" & userinfo.Email & "')" cmd.CommandType = CommandType.Text con.Open() intResult = cmd.ExecuteNonQuery() If intResult < 0 Then Return True Else Return False End If con.Close() con = Nothing End Function Public Function IsExist(ByVal userinfo As Model.UserInfo) As Boolean Dim con As SqlClient.SqlConnection = New SqlClient.SqlConnection(ConnectString) Dim cmd As SqlClient.SqlCommand Dim dalReader As SqlClient.SqlDataReader cmd = con.CreateCommand cmd.CommandText = "select * from Users where UserName='" & userinfo.UserName & "'" cmd.CommandType = CommandType.Text con.Open() dalReader = cmd.ExecuteReader() '判断数据是否已经存在 If dalReader.HasRows = True Then Return True Else Return False End If con.Close() con = Nothing End Function End Class
BLL层进行逻辑判断,并且实现UI和DAL层的数据交互:
Imports Add.DAL Imports Add.Model Public Class Manager Public Function Adduser(ByVal user As UserInfo) As Boolean Dim dao As New UserDAO Dim userinfo As New UserInfo If dao.IsExist(user) = True Then Return False Else dao.AddUser(user) Return True End If End Function End Class
UI层是用户操作的界面,为用户提供输入的界面和返回信息:
Imports Add.BLL Imports Add.Model Public Class Form1 Private Sub btnOK_Click(sender As Object, e As EventArgs) Handles btnOK.Click Dim AddStu As New Manager '实例化B层 Dim UStudent As New UserInfo '实例化实体类 If Trim(txtUserName.Text) = "" Then MessageBox.Show("请输入用户名") Exit Sub End If If Trim(txtPassword.Text) = "" Then MessageBox.Show("请输入密码") Exit Sub End If If Trim(txtPassword2.Text) = "" Then MessageBox.Show("请确认密码") Exit Sub End If If Trim(txtPassword.Text) <> Trim(txtPassword2.Text) Then MessageBox.Show("两次密码不相同,请重新输入") Exit Sub End If '将输入的数据存储到实体类,进行传值 UStudent.UserName = txtUserName.Text UStudent.Password = txtPassword.Text UStudent.Email = txtEmail.Text If AddStu.Adduser(UStudent) Then '用户不存在 MessageBox.Show("添加成功") Else '用户已经存在 MessageBox.Show("该用户已注册,请重新添加") End If End Sub Private Sub btnCancel_Click(sender As Object, e As EventArgs) Handles btnCancel.Click End End Sub End Class
执行程序:
总结:
通过这个小例子,让自己对三层的理解更加深刻,也知道了该如何运用它。原先停留在表面上的理解,至此也升华到了操作上。虽然先前有很多不理解的地方,但是通过实践,自己得到了理解。所以,当我们遇到问题的时候,不要仅仅去理解,要通过实践去做,只有真正做过之后才能真正理解。
时间: 2024-10-26 22:07:06