Dim conn As New OracleConnection(oradb)
        conn.Open()
        Dim cmd As New OracleCommand
        Dim testfile As String
        cmd.Connection = conn
        cmd.CommandType = CommandType.Text
        cmd.CommandText = ("select test,seqnum from msg.testvb where id = 1 and rownum = 1") 'seqnum тут получаю имя для файла
        cmd.ExecuteNonQuery()
        testfile = cmd.ExecuteScalar()
        IO.File.Create("C:/test.txt").Dispose()
        IO.File.WriteAllText("C:/test.txt", testfile, System.Text.Encoding.GetEncoding(1251)) 
        If IO.File.Exists("C:/test.txt") Then
            cmd.CommandText = ("update msg.testvb set id = 3 where id = 1")
            cmd.ExecuteNonQuery()
        End If
        cmd.Dispose()
        conn.Dispose()

   Dim oradb As String = "Data Source=jamocs;User Id=ocs;Password=_ocs;"
        Dim conn As New OracleConnection(oradb)
        conn.Open()
        Dim cmd As New OracleCommand
        Dim testfile As String
        'Dim tt As New IO.DirectoryInfo("c:\")
        cmd.Connection = conn
        cmd.CommandType = CommandType.Text
        cmd.CommandText = ("select seqnum from msg.testvb where id = 1 and rownum = 1")
        cmd.ExecuteNonQuery()
        testfile = cmd.ExecuteScalar()
        'IO.File.Create("C:/test.txt").Dispose()
        'My.Computer.FileSystem.RenameFile("C:/test.txt", testfile & ".txt")
        IO.File.WriteAllText(testfile & ".txt", testfile, System.Text.Encoding.GetEncoding(1251)) 'методом научного тыка получилось так, но данные в файл не попадают
        If IO.File.Exists("C:/test.txt") Then
            cmd.CommandText = ("update msg.testvb set id = 3 where id = 1")
            cmd.ExecuteNonQuery()
        End If
        cmd.Dispose()
        conn.Dispose()

 Dim tt As String
        tt = "c:\"
        IO.File.WriteAllText("tt " & testfile & ".txt", testfile, System.Text.Encoding.GetEncoding(1251))

cmd.CommandText = ("update msg.testvb set id = 3 where seqnum = :data")

("select test,seqnum from msg.testvb where id = 1 and rownum = 1")

 Dim oradb As String = "Data Source=jamocs;User Id=ocs;Password=_ocs;"
        Dim conn As New OracleConnection(oradb)
        conn.Open()
        Dim cmd As New OracleCommand
        Dim testfile As String
        Dim sFileName As String
        Dim data As String
        cmd.Connection = conn
        cmd.CommandType = CommandType.Text
        cmd.CommandText = ("select test,seqnum from msg.testvb where id = 1 and rownum = 1")
        Dim reader As OracleDataReader = cmd.ExecuteReader()
        While reader.Read()
            If reader.GetValue(1) > 0 Then    'тут пишет Оператор ">" не задан для тип "DBNull" и тип "Integer".
                data = reader.GetValue(1)
                sFileName = reader.GetValue(0)
                testfile = "C:\" & reader.GetValue(1) & ".txt"      'каталог для сохранения файлов
                IO.File.WriteAllText(testfile, sFileName, System.Text.Encoding.GetEncoding(1251))
                If IO.File.Exists(testfile) = True Then
                    cmd.CommandText = ("update msg.testvb set id = 3 where seqnum = :data")
                    cmd.Parameters.Add("data", OracleDbType.Varchar2).Value = data
                    cmd.ExecuteNonQuery()
                End If
            End If
        End While
        reader.Dispose()
        cmd.Dispose()
        conn.Dispose()