Dim txn As SqlTransaction
    Dim ds As New DataSet
    Dim con As New SqlConnection("Data source=sourcename;Initial catalog=Northwind;uid=gopi;pwd=gopi")
    Private Sub CmdFill_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CmdFill.Click
        con.Open()
        adp.Fill(ds, "Customers")
        txn = con.BeginTransaction(IsolationLevel.RepeatableRead)
        adp.SelectCommand.Transaction = txn
        adp.Fill(ds)
        DataGridView1.DataSource = ds
        DataGridView1.DataMember = "Customers"
    End Sub