Three-tier database "Check" four magic weapon

After completing these four functions feel "check" is the most simple of the four functions, the following to see how it is implemented:

The physical layer is not said to be the same as the first three functions.

UI layer:

<span style= "FONT-FAMILY:KAITI_GB2312;FONT-SIZE:24PX;" >public Class Form1    ' query    Private Sub btnlogin_click (sender as Object, e as EventArgs) Handles btnselect.click
   try            ' Gets the data for the presentation layer            Dim Muser as new Loginmodel.user              ' instantiates a new entity to pass the entity muser of Layer B            . UserName = TxtUserName.Text.Trim           ' passes the user name to the UserName Muser 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.SELECTBLL            Muser = Mgr. SELECTBLL (Muser)        Catch ex as Exception            MessageBox.Show (ex. Message.tostring ())              ' Error handling        end Try    end Sub   End class</span>

BLL layer:

<span style= "FONT-FAMILY:KAITI_GB2312;FONT-SIZE:24PX;" > SELECTBLL public    Function SELECTBLL (ByVal User as Loginmodel.user) as Loginmodel.user        Dim Udao as New Logindal.sqlserveruser ()               ' instantiates a new Userdao object in the D layer        Dim Muser as Loginmodel.user                  ' defines a type as the entity layer parameter, the user assigns the value        Muser = Udao.selectdal (User)        ' determines whether to query to record        if IsNothing (muser.username) then            Throw New Exception ("Query failed , please check your username and password! ")          ' did not record        Else            MsgBox (" The query succeeded, congratulations! "," cue box ")         ' has a record        end If        return Muser            ' returns the entity    end FunctionEnd class</span>

dal layer:

<span style= "FONT-FAMILY:KAITI_GB2312;FONT-SIZE:24PX;" > ' Referencing namespaces imports System.dataimports System.Data.SqlClientImports Loginmodel ' d layer, mainly on the original data (database or text files, such as the form of data storage) operation layer, need to refer to the physical layer ' public Class sqlserveruser public Conn as New SqlConnection (" Server=zy-pc;database=login;user Id=sa;password = 1 ") ' Create database connection public Function Selectdal (ByVal user as user) A        S loginmodel.user ' transfer entity login for easy invocation of parameters in entities Dim reader as SqlDataReader ' defines variable reader of type SqlDataReader Dim Muser As New Loginmodel.user Dim sql As String = "Select Username,password from T_users where [Email&nbs        P;protected] and [email protected] "database query statement Dim cmd as New SqlCommand (SQL, conn) ' Create SqlCommand Object Cmd. CommandText = SQL ' gets the concrete content of the SQL statement cmd. CommandType = CommandType.Text ' Gets the specific type of the above SQL statement, CMD. Parameters.Add (New SqlParameter ("@UserName", User.username)) cmd. Parameters.Add (New SqlParameter ("@PassWord", User.password)) Conn. Open () ' opens data connection reader = cmd. ExecuteReader () ' Executes the query statement and generates a DataReader ' read the query to the data and returns it to the corresponding property while reader. Read () Muser.username = reader. GetString ("UserName") ' assigns value to @username Muser.password = reader. GetString ("PassWord") ' assigns an End while return Muser ' to @password to return the entity conn to the query. Close () ' Closed connection End functionend class</span>

database Four magic weapons to this has all been introduced, of course, this is a three-tier database "natural to carve" the most basic, the most simple, but also need to undergo further processing and improvement.

Three-tier database "Check" four magic weapon