The "change" of the four key weapons of three-tier database

In this function I used two forms, one to get the original user number, and the other to get the current password, I would like to elaborate:

Similarly, the entity layer:

<span style= "FONT-FAMILY:KAITI_GB2312;FONT-SIZE:24PX;" > ' <summary> ' entity layer, storing multiple properties ' </summary> ' ' <remarks></remarks>public Class User    ' Defines the UserName property    Private _username As String public property    UserName As String        Get            Return _username        End Get        Set (value as String)            _username = value        End Set    End    Property ' Define password attribute    Private _ PassWord As String ' public property    PassWord As String        get            Return _password        End Get        Set (value As String)            _password = value        end Set    end Propertyend class</span>

UI Layer:

First form:

<span style= "FONT-FAMILY:KAITI_GB2312;FONT-SIZE:24PX;" >public Class Form1    '    Private Sub btnchange_click (sender as Object, e as EventArgs) Handles btnchange.click
   frmchange.show ()                ' Call the changed form    End subend class</span>

a second form:

<span style= "FONT-FAMILY:KAITI_GB2312;FONT-SIZE:24PX;" >public Class frmchange    Private Sub button1_click (sender as Object, e as EventArgs) Handles Btnchange.click        Tr Y            ' get data for the presentation layer            Dim Nuser as new Loginmodel.user              ' instantiates a new entity that is used to pass the entity nuser of Layer B            . UserName = TxtUserName.Text.Trim           ' passes the user name to the UserName nuser of the entity layer            . PassWord = TxtPassWord.Text.Trim            ' Pass the password to the entity layer PassWord            ' call layer B, login to determine            Dim Mgr as New Loginbll.usermananger Call            Mgr. CHANGEBLL (nuser)        Catch ex as Exception            MessageBox.Show (ex. Message.tostring ())              ' Error handling        end Try    End SubEnd class</span>

BLL layer:

<span style= "FONT-FAMILY:KAITI_GB2312;FONT-SIZE:24PX;" >public Class usermananger    ' change public    Sub CHANGEBLL (ByVal User as Loginmodel.user)        Dim Udao as New logindal . Sqlserveruser        ' query if the user exists, if there is a change password, if there is no prompt box        Dim muser as Loginmodel.user call        udao.changdal (user)        if IsNothing (muser.username)            then MsgBox ("User not present, re-enter", "warning")        Else call            udao.changdal (user)            Invoke Modify function        end If    End SubEnd class</span>

<span style= "Background-color:rgb (255, 255, 255); ><span style= "Font-family:kaiti_gb2312;font-size:24px;color: #3333ff;" ><strong>dal Layer:</strong></span></span>

<span style= "Background-color:rgb (255, 255, 255);" ></span><pre name= "code" class= "VB" ><span style= "FONT-FAMILY:KAITI_GB2312;FONT-SIZE:24PX;"  > ' Reference namespaces Imports System.dataimports System.Data.SqlClientImports loginmodelpublic Class sqlserveruser Public Conn as New SqlConnection ("Server=zy-pc;database=login;user Id=sa;password = 1") ' Create database connection ' to public Sub changdal (B        Yval user as user) Dim sql as String = "Update t_users set [email protected] where [email protected]" The SQL statement for the update number library is Dim cmd as New SqlCommand (SQL, conn) cmd. CommandText = sql cmd. CommandType = CommandType.Text cmd. Parameters.Add (New SqlParameter ("@User", User.username)) cmd. Parameters.Add (New SqlParameter ("@PassWord", User.password)) Conn. Open () cmd. ExecuteNonQuery () ' performs an operation on the database Conn. Close () End subend Class</span> 

The "change" of the four key weapons of three-tier database