Вывод данных из SQL 2008 на форму

Private Sub Form1_Load(sender As Object, e As System.EventArgs) Handles Me.Load
        Dim conn1 As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|\db.mdb"
        Dim cmd1 As String = "SELECT  p1 FROM tab1"
        Dim dt As New DataTable
        Dim DR As New Data.OleDb.OleDbDataAdapter(cmd1, conn1)
        DR.Fill(dt)
 
        For i As Integer = 0 To dt.Rows.Count - 1
            ComboBox1.Items.Add(dt.Rows(i)(0))
 
        Next
    End Sub
    Private Sub ComboBox1_SelectedIndexChanged(sender As System.Object, e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged
        Dim conn1 As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|\db.mdb"
        Dim cmd1 As String = "SELECT p2 FROM tab1 WHERE p1='" & ComboBox1.Text & "'"
        Dim dt As New DataTable
        Dim DR As New Data.OleDb.OleDbDataAdapter(cmd1, conn1)
        DR.Fill(dt)
 
        For i As Integer = 0 To dt.Rows.Count - 1
            ComboBox2.Items.Add(dt.Rows(i)(0))
            
        Next
    End Sub
 
    Private Sub ComboBox2_SelectedIndexChanged(sender As System.Object, e As System.EventArgs) Handles ComboBox2.SelectedIndexChanged
        Dim conn1 As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|\db.mdb"
        Dim cmd1 As String = "SELECT p3,p4  FROM tab1 WHERE ((p1='" & ComboBox1.Text & "') and (p2='" & ComboBox2.Text & "'))"
        Dim dt As New DataTable
        Dim DR As New Data.OleDb.OleDbDataAdapter(cmd1, conn1)
        DR.Fill(dt)
 
        For i As Integer = 0 To dt.Rows.Count - 1
            ComboBox3.Items.Add(dt.Rows(i)(0))
            ComboBox4.Items.Add(dt.Rows(i)(1))
 
        Next
    End Sub