ขอถามเรื่อง DataGridView หน่อยครับ VB2008 กับ Oracle

Imports System.Data

Imports System.Data.OracleClient
Public Class Form4
    Dim strConn As String
    Dim Conn As OracleConnection
    Dim cmd As OracleCommand
    Dim dr As OracleDataReader
    Dim dt As DataTable
    Dim ds As New DataSet
    Dim Sql As String

    Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button5.Click
        Conn = New OracleConnection(strConn)
        Conn.Open()
        Sql = "select * from computer_service order by cs_id"

        cmd = New OracleCommand(Sql, Conn)

        dr = cmd.ExecuteReader

        If dr.HasRows Then
            dt = New DataTable
            dt.Load(dr)
            DataGridView1.DataSource = dt
        Else
            MessageBox.Show("No Data !!")
            Exit Sub
        End If


        Conn.Close()
    End Sub

    Private Sub Form4_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        strConn = "Data Source=ambassader;User Id=ambassader;Password=Amb12;"
        Conn = New OracleConnection(strConn)
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Try
            Conn.Open()
            Sql = "INSERT INTO COMPUTER_SERVICE values('" & TextBox1.Text() & "','" & TextBox2.Text() & "','" & MaskedTextBox2.Text() & "',TO_DATE('" & MaskedTextBox1.Text() & "','yyyy-mm-dd'))"
            'MessageBox.Show(Sql)"
            cmd = New OracleCommand(Sql, Conn)
            cmd.ExecuteNonQuery()
            TextBox4.Visible = False
            TextBox3.Visible = True
            'MessageBox.Show("Insert Complete")"
            Conn = New OracleConnection(strConn)
            Conn.Open()
            Sql = "select * from computer_service order by cs_id"
            cmd = New OracleCommand(Sql, Conn)

            dr = cmd.ExecuteReader

            If dr.HasRows Then
                dt = New DataTable
                dt.Load(dr)
                DataGridView1.DataSource = dt
            Else
                MessageBox.Show("No Data !!")
                Exit Sub
            End If


            Conn.Close()


        Catch ex As OracleException
            MessageBox.Show("Insert Incomplete : กรุณาตรวจสอบข้อมูลการป้อน")
            'MessageBox.Show("Case : " & ex.ToString())
            Exit Sub
        Finally
            Conn.Close()
        End Try
    End Sub

    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        Try
            Conn.Open()
            Sql = "delete computer_service where cs_id = ('" & TextBox1.Text() & "')"
            'MessageBox.Show(Sql)"
            cmd = New OracleCommand(Sql, Conn)
            cmd.ExecuteNonQuery()
            TextBox3.Visible = False
            TextBox4.Visible = True
            'MessageBox.Show("Delete Complete")"
            Conn = New OracleConnection(strConn)
            Conn.Open()
            Sql = "select * from computer_service order by cs_id"

            cmd = New OracleCommand(Sql, Conn)

            dr = cmd.ExecuteReader

            If dr.HasRows Then
                dt = New DataTable
                dt.Load(dr)
                DataGridView1.DataSource = dt
            Else
                MessageBox.Show("No Data !!")
                Exit Sub
            End If


            Conn.Close()

        Catch ex As OracleException
            MessageBox.Show("Delete Incomplete : กรุณาตรวจสอบข้อมูล")
            'MessageBox.Show("Case : " & ex.ToString())
            Exit Sub
        Finally
            Conn.Close()
        End Try
    End Sub

End Class