مشكلة في كود الإضافة والتعديل والحذف

Private m_cnADONetConnection As New OleDb.OleDbConnection()
Private m_daDataAdapter As New OleDb.OleDbDataAdapter
Private m_cbCommandBuilder As OleDb.OleDbCommandBuilder
Private test1 As New DataTable
Private m_rowPosition As Integer = 0

Private Sub Form1_FormClosed(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosedEventArgs) Handles Me.FormClosed
m_cnADONetConnection.Close()
m_cnADONetConnection.Dispose()
End Sub

Private Sub ShowCurrentRecord()
If test1.Rows.Count = 0 Then
name1.Text = ""
no.Text = ""
Exit Sub
End If

name1.Text = _
test1.Rows(m_rowPosition)("name1").ToString()
no.Text = _
test1.Rows(m_rowPosition)("no").ToString()
End Sub

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
m_cnADONetConnection.ConnectionString = _
"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\temp\test.mdb"
m_cnADONetConnection.Open()

m_daDataAdapter = _
New OleDb.OleDbDataAdapter("Select * From test1", m_cnADONetConnection)

m_cbCommandBuilder = New OleDb.OleDbCommandBuilder(m_daDataAdapter)

m_daDataAdapter.Fill(test1)

Me.ShowCurrentRecord()
End Sub

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
m_rowPosition = 0
Me.ShowCurrentRecord()
End Sub

Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
If m_rowPosition > 0 Then
m_rowPosition = m_rowPosition - 1
Me.ShowCurrentRecord()
End If
End Sub

Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
If m_rowPosition < (test1.Rows.Count - 1) Then
m_rowPosition = m_rowPosition + 1
Me.ShowCurrentRecord()
End If
End Sub

Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click
If test1.Rows.Count > 0 Then
m_rowPosition = test1.Rows.Count - 1
Me.ShowCurrentRecord()
End If
End Sub

Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button5.Click
If test1.Rows.Count <> 0 Then
test1.Rows(m_rowPosition)("name1") = name1.Text
test1.Rows(m_rowPosition)("no") = no.Text
m_daDataAdapter.Update(test1)
End If
End Sub

Private Sub Button6_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button6.Click
Dim drNewRow As DataRow = test1.NewRow

drNewRow("name1") = TextBox3.Text
drNewRow("no") = TextBox4.Text
test1.Rows.Add(drNewRow)
m_daDataAdapter.Update(test1)
m_rowPosition = test1.Rows.Count - 1
Me.ShowCurrentRecord()
End Sub
End Class

Public Class Form1