Try
            Dim conn As New OracleConnection("Data Source=lvbocs;User Id=msg;Password=msg;")
            Dim cmd As New OracleCommand
            cmd.CommandText = "select * from test.T_SUMM"
            conn.Open()
            cmd.Connection = conn
            Dim oradtreader As OracleDataReader = cmd.ExecuteReader(CommandBehavior.CloseConnection)
            If IO.File.Exists("C:\test.txt") = True Then
                IO.File.Delete("C:\test.txt")
            End If

            While oradtreader.Read = True
                Dim i, sum, sum2, i2 As String
                i = oradtreader.GetValue(0)
                i2 = oradtreader.GetValue(1)
                sum = i + 
                sum2 = i2 +
                Dim wr As StreamWriter
                wr = File.AppendText("C:\test.txt")
                wr.WriteLine(sum & ";" & sum2)
                wr.Flush()
                wr.Close()
            End While
            oradtreader.Close()
            conn.Close()
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try

 Dim table As New DataTable
            table.Columns.Add("Orders")
            While oradtreader.Read = True
                table.Rows.Add(oradtreader.GetValue(0))
            End While
            Dim sumObject As Object
            sumObject = table.Compute("Orders", ) ' не знаю что сюда вставить, пишут про фильтр, а если мне не нужно ограничиваться строками?

            table.Rows.Add("TOTAL" & sumObject)
            DataGridView1.DataSource = table

 sumObject = table.Compute("Orders", "Orders >0")