Private Sub btnAdd_Click(sender As Object,e As EventArgs) Handles btnAdd.Click '添加按钮
        Dim ADDStu As New StuBLL.ManageBLL  '实例化B层的类ManageBLL，实现对B层的引用
        Dim Ustudent As New StuEntity.StudentEntity '实例化实体层类StudentEntity，方便存储参数
        '对文本框的输入做限制
        If Trim(txtID.Text) = "" Or IsNumeric(Trim(txtID.Text)) = False Then
            MessageBox.Show("请输入合适学号，再进行该操作")
            Exit Sub
        End If
        If Trim(txtName.Text) = "" Then
            MessageBox.Show("请输入姓名，再进行该操作")
            Exit Sub
        End If
        If Trim(txtTel.Text) = "" Or IsNumeric(Trim(txtTel.Text)) = False Then
            MessageBox.Show("请输入联系电话，再进行该操作")
            Exit Sub
        End If
        '给实体类的属性赋值
        Ustudent.StuID = CInt((txtID.Text))
        Ustudent.StuMarks = Trim(CStr(txtName.Text))
        Ustudent.StuTel = CDec(txtTel.Text)
        '调用类方法 AddStuManager 并报告
        If ADDStu.AddStuManager(Ustudent) Then
            MessageBox.Show("添加成功，请刷新")
        Else
            MessageBox.Show("该学号已添加，请重新添加")

        End If

    End Sub

Imports StuDAL
Imports StuEntity
Public Class ManageBLL
    Public Function AddStuManager(ByVal stuInfoEn As StuEntity.StudentEntity) As Boolean '判断可否插入信息，并返回布尔值
        Dim Controller As New StuDAL.sqlDAL   '实例化D层类sqlDAL，完成对D层的引用
        Dim StuInfo As New StuEntity.StudentEntity   '引用实体类，以便储存一定的参数

        If Controller.IsExist(stuInfoEn) = True Then   '根据ID判断该条记录是否已经存在，若存在返回False
            Return False
        Else                                        '若不存在，执行添加的方法，并返回True
            Controller.AddStu(stuInfoEn)
            Return True
        End If
    End Function
End Class

Imports StuEntity
Public Class sqlDAL
    Public Function AddStu(ByVal stuinfoen As StuEntity.StudentEntity) As Boolean '根据传入的参数StudentEntity，执行 数据库 插入命令 并返回布尔值

        Dim con As sqlClient.sqlConnection
        Dim cmd As sqlClient.sqlCommand
        Dim intResult As Integer

        con = New sqlClient.sqlConnection(ContactDAL.sqlString())  ‘建立对数据库的连接
        cmd = con.CreateCommand()

        cmd.CommandText = "insert into T_Names (ID,Name,Tel) values (" & stuinfoen.StuID & ",'" & stuinfoen.StuMarks & "'," & stuinfoen.StuTel & ")"  ’对数据中数据操作的具体sql语句
        cmd.CommandType = CommandType.Text
        con.Open()   ‘打开对数据库的连接
        intResult = cmd.ExecuteNonQuery()   ，执行sql语句，并返回执行结果
        If intResult < 0 Then   ，如果操作成功，则返回True，失败则返回False
            Return True
        Else
            Return False
        End If
        con.Close()   ’关闭连接，
        con = Nothing   ，清楚存储
    End Function
    Public Function IsExist(ByVal stuinfoen As StuEntity.StudentEntity) As Boolean  '根据传入的参数StudentEntity，执行数据查询命令，检查是否有要检索的内容
        Dim con As sqlClient.sqlConnection = New sqlClient.sqlConnection(ContactDAL.sqlString())
        Dim cmd As sqlClient.sqlCommand
        Dim dalReader As sqlClient.sqlDataReader

        cmd = con.CreateCommand
        cmd.CommandText = "select *from T_Names where ID='" & stuinfoen.StuID & "'"
        cmd.CommandType = CommandType.Text
        con.Open()
        dalReader = cmd.ExecuteReader()

        If dalReader.HasRows = True Then
            Return True
        Else
            Return False
        End If
        con.Close()
        con = Nothing
    End Function
End Class

'定义实体类，存储数据表T_Names中的数据
Public Class StudentEntity       '声明私有字段
    Private _StuID As Integer
    Private _StuMark As String
    Private _StuTel As Integer

    Property StuID As Integer    '定义StuId属性
        Get
            Return _StuID
        End Get
        Set(value As Integer)
            _StuID = value
        End Set
    End Property
    Property StuMarks As String   '定义StuMarks属性
        Get
            Return _StuMark
        End Get
        Set(value As String)
            _StuMark = value
        End Set
    End Property
    Property StuTel As Integer   '定义StuTel属性
        Get
            Return _StuTel
        End Get
        Set(value As Integer)
            _StuTel = value
        End Set
    End Property
End Class