データの読み出し（read）

  Const GET_VALUE_SQL_BASE As String = "select datetime, value from t_value " & _
                                       " where term = :term and company_id = :company_id and market_id = " & GET_MARKET_ID_SQL & _
                                       " and category_id = " & GET_CATEGORY_ID_SQL & " and item_id = " & GET_ITEM_ID_SQL

  Const GET_VALUE_SQL As String = GET_VALUE_SQL_BASE & " ORDER BY datetime DESC;"

  Protected _readCom As NpgsqlCommand

  Sub New()
    _readCom = New NpgsqlCommand(GET_VALUE_SQL, _conn)
    _readCom.Parameters.Add(New NpgsqlParameter("term", DbType.String))
    _readCom.Parameters.Add(New NpgsqlParameter("company_id", DbType.Int32))
    _readCom.Parameters.Add(New NpgsqlParameter("market_name", DbType.String))
    _readCom.Parameters.Add(New NpgsqlParameter("category_name", DbType.String))
    _readCom.Parameters.Add(New NpgsqlParameter("item_name", DbType.String))
    _readCom.Prepare()
  End Sub

  Function FindList(ByVal term As String, ByVal company_id As Integer, ByVal market As Entity.Market.IStockMarket, ByVal category_name As String, _
               ByVal item_name As String) As List(Of SeqValue)

    _readCom.Parameters("term").Value = term
    _readCom.Parameters("company_id").Value = company_id
    _readCom.Parameters("market_name").Value = market.DBItemName
    _readCom.Parameters("category_name").Value = category_name
    _readCom.Parameters("item_name").Value = item_name

    Dim dr As NpgsqlDataReader = _readCom.ExecuteReader()
    Dim list As List(Of SeqValue) = GetData(dr, term, company_id, market, category_name, item_name)
    dr.Close()

    Return list
  End Function

  Private Shared Function GetData(ByVal dr As NpgsqlDataReader, ByVal term As String, ByVal company_id As Integer, ByVal market As IStockMarket, ByVal category_name As String, ByVal item_name As String) As List(Of SeqValue)

    Dim list As New List(Of SeqValue)

    Do While dr.Read
      Dim sv As New SeqValue
      sv.term = term
      sv.company_id = company_id
      sv.market = market
      sv.category_name = category_name
      sv.item_name = item_name
      sv.datetime = DirectCast(dr.Item("datetime"), Date)
      sv.value = DirectCast(dr.Item("value"), Double)
      list.Add(sv)
    Loop

    Return list
  End Function

Dim dao As New SeqValueDAO
Dim list As List(Of SeqValue) = dao.FindList(term ,company_id, market, category_name, item_name)