add records to access database

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VB

Iam new to vb.net programming.I want to add records to an access database table. I get the error message "NullReferenceException was unhandled" when using the following code.Can anyone
help to correct this.

Dim con As New OleDb.OleDbConnection
        Dim dbProvider As String
        Dim dbSource As String
        Dim ds As New DataSet

        Dim da As OleDb.OleDbDataAdapter
        Dim sql As String
        Dim inc As Integer
        dbProvider = "provider=microsoft.ACE.OLEDB.12.0;"
        dbSource = "DATA SOURCE=C:\cwhData\cwhData.accdb"
        con.ConnectionString = dbProvider & dbSource
        con.Open()
        sql = "select * from customer"
        da = New OleDb.OleDbDataAdapter(sql, con)
        If inc <> -1 Then
            Dim cb As New OleDb.OleDbCommandBuilder(da)

            Dim dsNewRow As DataRow
            dsNewRow = ds.Tables("customer").NewRow()
            dsNewRow.Item("CUSTOMERID") = txtCustomerID.Text
            dsNewRow.Item("customername") = txtCustomerName.Text
            ds.Tables("customer").Rows.Add(dsNewRow)
            da.Update(ds, "customer")
            MsgBox("New record added to the database")



        End If
        MsgBox("database is now open")
        con.Close()
        MsgBox("database is now closed")
    End Sub