同一インターフェイスで4種のDBクラス

同一インターフェイスで4種のDBクラス

データベース

Odbc、OleDb、OracleClient、SqlClient

フレームワークには4種類のDB用のクラスがありますが、細かいところはともかく、
基本的な処理は同じで、通常の更新処理や読み込み処理はそれほど多くない
メソッドで事足ります。

また、同一インターフェイスにしておけば、どのDB を使用しているかに関わらず
コードを書く事ができます
( Object に代入してしまえば同じですが、インターフェイスだと候補ウインドウが使えます )

Private myOwner As Object = Nothing
Private db As DbInterface

Private Sub Dialog1_Load(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles MyBase.Load

	myOwner = Me.Owner

End Sub

' ******************************************************
' 処理
' ******************************************************
Private Sub 処理_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles 処理.Click

	' 親ウインドウの DB を参照( 同一インターフェイス )
	db = myOwner.db

	If Not db.Connect() Then
		Console.WriteLine(db.myError)
		Return
	End If

	db.QueryAndRead("SELECT * from 社員マスタ where 社員コード = '0001'")
	MessageBox.Show(db.GetValue("氏名"))

	db.Close()

End Sub

コード

Imports System.Data.OleDb
Imports System.Data.Odbc
Imports System.Data.OracleClient
Imports System.Data.SqlClient

' ******************************************************
' DB アクセス用インターフェイス
' ******************************************************
Interface DbInterface

	ReadOnly Property myError() As String
	ReadOnly Property myConnectString() As String
	ReadOnly Property SqlString() As String

	Function Connect() As Boolean
	Function Query(ByVal SQL As String) As Boolean
	Function Read() As Boolean
	Function QueryAndRead(ByVal SQL As String) As Boolean
	Function Execute(ByVal SQL As String) As Integer
	Function GetValue(ByVal ColumnName As String) As String
	Function GetDate(ByVal ColumnName As String) As String
	Sub Close()

End Interface

' ******************************************************
' Oracle
' ******************************************************
Public Class DbOracle
	Implements DbInterface

	' ******************************************************
	' 内部変数( プロパティ )
	' ※ Public は、開発中なので都合がいいように
	' ******************************************************
	Public _myConnectString As String = Nothing
	Public myCon As OracleConnection = Nothing
	Public myCommand As OracleCommand = New OracleCommand()
	Public myReader As OracleDataReader = Nothing
	Public _myError As String = ""
	Public _SqlString As String = ""

	Public ReadOnly Property myConnectString() As String _
	  Implements DbInterface.myConnectString
		Get
			Return _myConnectString
		End Get
	End Property

	Public ReadOnly Property myError() As String _
	  Implements DbInterface.myError
		Get
			Return _myError
		End Get
	End Property

	Public ReadOnly Property SqlString() As String _
	  Implements DbInterface.SqlString
		Get
			Return _SqlString
		End Get
	End Property

	' ******************************************************
	' コンストラクタ
	' ******************************************************
	Public Sub New( _
	 ByVal sv As String, _
	 ByVal user As String, _
	 ByVal pass As String)

		Me._myConnectString = _
		 "Server=" + sv + ";" + _
		 "User ID=" + user + ";" + _
		 "Password=" + pass + ";"

	End Sub

	' ******************************************************
	' 接続
	' ******************************************************
	Public Function Connect() As Boolean _
	 Implements DbInterface.Connect

		Dim ret As Boolean

		Me.myCon = New OracleConnection()
		Me.myCon.ConnectionString = Me.myConnectString

		Try
			Me.myCon.Open()
			Me.myCommand.Connection = Me.myCon
			ret = True
		Catch ex As Exception
			Me.myCon = Nothing
			Me._myError = "接続エラーです" + ControlChars.CrLf
			Me._myError += "接続文字列=" + Me.myConnectString + ControlChars.CrLf
			Me._myError += "システムのメッセージ=" + ex.Message + ControlChars.CrLf
			ret = False
		End Try

		Return ret

	End Function

	' ******************************************************
	' SQL を実行して読み込みの準備
	' ※ OleDbDataReader を作成
	' ******************************************************
	Public Function Query(ByVal SQL As String) As Boolean _
	 Implements DbInterface.Query

		Me._SqlString = SQL

		Dim ret As Boolean

		' 読み取りオブジェクトが閉じていない場合は、閉じる
		If Not Me.myReader Is Nothing Then
			If Not Me.myReader.IsClosed Then
				Me.myReader.Close()
			End If
		End If

		Me.myCommand.CommandText = SQL

		Try
			Me.myReader = myCommand.ExecuteReader()
			ret = True
		Catch ex As Exception
			Me._myError = ex.Message
			ret = False
		End Try

		Return ret

	End Function

	' ******************************************************
	' 1行読み込む
	' ※ データが無くなると False を返す
	' ******************************************************
	Public Function Read() As Boolean _
	 Implements DbInterface.Read

		If Not Me.myReader Is Nothing Then
			If Not Me.myReader.IsClosed Then
				Return Me.myReader.Read()
			Else
				Me._myError = "Reader は閉じられています"
				Return False
			End If
		Else
			Me._myError = "Query が一度も実行されていません"
			Return False
		End If

	End Function

	' ******************************************************
	' SQL を実行して1行読み込む
	' ******************************************************
	Public Function QueryAndRead(ByVal SQL As String) As Boolean _
	 Implements DbInterface.QueryAndRead

		Dim ret As Boolean

		ret = Me.Query(SQL)
		If ret Then
			ret = Me.Read()
		End If

		Return ret

	End Function

	' ******************************************************
	' UPDATE、INSERT、および DELETE を実行する
	' 戻り値は影響を受けた行数
	' -1 は他の SQL を実行した場合
	' -2 はエラー
	' ******************************************************
	Public Function Execute(ByVal SQL As String) As Integer _
	 Implements DbInterface.Execute

		Me._SqlString = SQL

		Dim ret As Integer
		Dim execCommand As OracleCommand = New OracleCommand()

		execCommand.CommandText = SQL
		execCommand.Connection = Me.myCon
		Try
			ret = execCommand.ExecuteNonQuery()
		Catch ex As Exception
			ret = -2
			Me._myError = ex.Message
		End Try
		execCommand.Dispose()

		Return ret

	End Function

	' ******************************************************
	' 指定した列名より文字列として値を得る
	' ******************************************************
	Public Function GetValue(ByVal ColumnName As String) As String _
	 Implements DbInterface.GetValue
		Dim ret As String = ""
		Dim fld As Integer = 0

		fld = Me.myReader.GetOrdinal(ColumnName)
		If Me.myReader.IsDBNull(fld) Then
			ret = ""
		Else
			ret = Me.myReader.GetValue(fld).ToString()
		End If

		Return ret
	End Function

	' ******************************************************
	' 日付時間型として、日付部分を文字列として値を得る
	' ******************************************************
	Public Function GetDate(ByVal ColumnName As String) As String _
	 Implements DbInterface.GetDate
		Dim ret As String = ""
		Dim fld As Integer = 0

		fld = Me.myReader.GetOrdinal(ColumnName)
		If Me.myReader.IsDBNull(fld) Then
			ret = ""
		Else
			Try
				ret = Me.myReader.GetDateTime(fld).ToString("d")
			Catch ex As Exception
				ret = ""
				Me._myError = ex.Message
			End Try
		End If

		Return ret
	End Function

	' ******************************************************
	' 接続解除
	' ******************************************************
	Public Sub Close() _
	 Implements DbInterface.Close

		' 読み取りオブジェクトが閉じていない場合は、閉じる
		If Not Me.myReader Is Nothing Then
			If Not Me.myReader.IsClosed Then
				Me.myReader.Close()
			End If
		End If

		If Not Me.myCon Is Nothing Then
			' 接続を閉じる
			Me.myCon.Close()

			' リソースの開放
			Me.myCon.Dispose()
			Me.myCommand.Dispose()

			' 次に備えて初期化
			Me.myCon = Nothing
		End If

	End Sub

End Class

' ******************************************************
' ODBC
' ******************************************************
Public Class DbOdbc
	Implements DbInterface

	' ******************************************************
	' 内部変数( プロパティ )
	' ※ Public は、開発中なので都合がいいように
	' ******************************************************
	Public _myConnectString As String = Nothing
	Public myCon As OdbcConnection = Nothing
	Public myCommand As OdbcCommand = New OdbcCommand()
	Public myReader As OdbcDataReader = Nothing
	Public _myError As String = ""
	Public _SqlString As String = ""

	Public ReadOnly Property myConnectString() As String _
	  Implements DbInterface.myConnectString
		Get
			Return _myConnectString
		End Get
	End Property

	Public ReadOnly Property myError() As String _
	  Implements DbInterface.myError
		Get
			Return _myError
		End Get
	End Property

	Public ReadOnly Property SqlString() As String _
	  Implements DbInterface.SqlString
		Get
			Return _SqlString
		End Get
	End Property

	' ******************************************************
	' コンストラクタ
	' ******************************************************
	Public Sub New( _
	 ByVal driver As String, _
	 ByVal sv As String, _
	 ByVal db As String, _
	 ByVal user As String, _
	 ByVal pass As String)

		Me._myConnectString = _
		 "Driver={" + driver + "};" + _
		 "SERVER=" + sv + ";" + _
		 "DATABASE=" + db + ";" + _
		 "UID=" + user + ";" + _
		 "PWD=" + pass + ";"

	End Sub

	' ******************************************************
	' 接続
	' ******************************************************
	Public Function Connect() As Boolean _
	  Implements DbInterface.Connect

		Dim ret As Boolean

		Me.myCon = New OdbcConnection()
		Me.myCon.ConnectionString = Me.myConnectString

		Try
			Me.myCon.Open()
			Me.myCommand.Connection = Me.myCon
			ret = True
		Catch ex As Exception
			Me.myCon = Nothing
			Me._myError = "接続エラーです" + ControlChars.CrLf
			Me._myError += "接続文字列=" + Me.myConnectString + ControlChars.CrLf
			Me._myError += "システムのメッセージ=" + ex.Message + ControlChars.CrLf
			ret = False
		End Try

		Return ret

	End Function


	' ******************************************************
	' SQL を実行して読み込みの準備
	' ※ OleDbDataReader を作成
	' ******************************************************
	Public Function Query(ByVal SQL As String) As Boolean _
	 Implements DbInterface.Query

		Me._SqlString = SQL

		Dim ret As Boolean

		' 読み取りオブジェクトが閉じていない場合は、閉じる
		If Not Me.myReader Is Nothing Then
			If Not Me.myReader.IsClosed Then
				Me.myReader.Close()
			End If
		End If

		Me.myCommand.CommandText = SQL

		Try
			Me.myReader = myCommand.ExecuteReader()
			ret = True
		Catch ex As Exception
			Me._myError = ex.Message
			ret = False
		End Try

		Return ret

	End Function

	' ******************************************************
	' 1行読み込む
	' ※ データが無くなると False を返す
	' ******************************************************
	Public Function Read() As Boolean _
	 Implements DbInterface.Read

		If Not Me.myReader Is Nothing Then
			If Not Me.myReader.IsClosed Then
				Return Me.myReader.Read()
			Else
				Me._myError = "Reader は閉じられています"
				Return False
			End If
		Else
			Me._myError = "Query が一度も実行されていません"
			Return False
		End If

	End Function

	' ******************************************************
	' SQL を実行して1行読み込む
	' ******************************************************
	Public Function QueryAndRead(ByVal SQL As String) As Boolean _
	 Implements DbInterface.QueryAndRead

		Dim ret As Boolean

		ret = Me.Query(SQL)
		If ret Then
			ret = Me.Read()
		End If

		Return ret

	End Function

	' ******************************************************
	' UPDATE、INSERT、および DELETE を実行する
	' 戻り値は影響を受けた行数
	' -1 は他の SQL を実行した場合
	' -2 はエラー
	' ******************************************************
	Public Function Execute(ByVal SQL As String) As Integer _
	 Implements DbInterface.Execute

		Me._SqlString = SQL

		Dim ret As Integer
		Dim execCommand As OdbcCommand = New OdbcCommand()

		execCommand.CommandText = SQL
		execCommand.Connection = Me.myCon
		Try
			ret = execCommand.ExecuteNonQuery()
		Catch ex As Exception
			ret = -2
			Me._myError = ex.Message
		End Try
		execCommand.Dispose()

		Return ret

	End Function

	' ******************************************************
	' 指定した列名より文字列として値を得る
	' ******************************************************
	Public Function GetValue(ByVal ColumnName As String) As String _
	 Implements DbInterface.GetValue

		Dim ret As String = ""
		Dim fld As Integer = 0

		fld = Me.myReader.GetOrdinal(ColumnName)
		If Me.myReader.IsDBNull(fld) Then
			ret = ""
		Else
			ret = Me.myReader.GetValue(fld).ToString()
		End If

		Return ret
	End Function

	' ******************************************************
	' 日付時間型として、日付部分を文字列として値を得る
	' ******************************************************
	Public Function GetDate(ByVal ColumnName As String) As String _
	 Implements DbInterface.GetDate

		Dim ret As String = ""
		Dim fld As Integer = 0

		fld = Me.myReader.GetOrdinal(ColumnName)
		If Me.myReader.IsDBNull(fld) Then
			ret = ""
		Else
			Try
				ret = Me.myReader.GetDateTime(fld).ToString("d")
			Catch ex As Exception
				ret = ""
				Me._myError = ex.Message
			End Try
		End If

		Return ret
	End Function

	' ******************************************************
	' 接続解除
	' ******************************************************
	Public Sub Close() _
	 Implements DbInterface.Close

		' 読み取りオブジェクトが閉じていない場合は、閉じる
		If Not Me.myReader Is Nothing Then
			If Not Me.myReader.IsClosed Then
				Me.myReader.Close()
			End If
		End If

		If Not Me.myCon Is Nothing Then
			' 接続を閉じる
			Me.myCon.Close()

			' リソースの開放
			Me.myCon.Dispose()
			Me.myCommand.Dispose()

			' 次に備えて初期化
			Me.myCon = Nothing
		End If

	End Sub

End Class

' ******************************************************
' MDB
' ******************************************************
Public Class DbAccess
	Implements DbInterface

	' ******************************************************
	' 内部変数( プロパティ )
	' ※ Public は、開発中なので都合がいいように
	' ******************************************************
	Public _myConnectString As String = Nothing
	Public myCon As OleDbConnection = Nothing
	Public myCommand As OleDbCommand = New OleDbCommand()
	Public myReader As OleDbDataReader = Nothing
	Public _myError As String = ""
	Public _SqlString As String = ""

	Public ReadOnly Property myConnectString() As String _
	  Implements DbInterface.myConnectString
		Get
			Return _myConnectString
		End Get
	End Property

	Public ReadOnly Property myError() As String _
	  Implements DbInterface.myError
		Get
			Return _myError
		End Get
	End Property

	Public ReadOnly Property SqlString() As String _
	  Implements DbInterface.SqlString
		Get
			Return _SqlString
		End Get
	End Property

	' ******************************************************
	' コンストラクタ
	' ******************************************************
	Public Sub New(ByVal dbpath As String)

		Me._myConnectString = _
		 "Provider=Microsoft.Jet.OLEDB.4.0;" + _
		 "Data Source=" + dbpath + ";"

	End Sub

	' ******************************************************
	' 接続
	' ******************************************************
	Public Function Connect() As Boolean _
	 Implements DbInterface.Connect

		Dim ret As Boolean

		Me.myCon = New OleDbConnection()
		Me.myCon.ConnectionString = Me.myConnectString

		Try
			Me.myCon.Open()
			Me.myCommand.Connection = Me.myCon
			ret = True
		Catch ex As Exception
			Me.myCon = Nothing
			Me._myError = "接続エラーです" + ControlChars.CrLf
			Me._myError += "接続文字列=" + Me.myConnectString + ControlChars.CrLf
			Me._myError += "システムのメッセージ=" + ex.Message + ControlChars.CrLf
			ret = False
		End Try

		Return ret

	End Function


	' ******************************************************
	' SQL を実行して読み込みの準備
	' ※ OleDbDataReader を作成
	' ******************************************************
	Public Function Query(ByVal SQL As String) As Boolean _
	 Implements DbInterface.Query

		Me._SqlString = SQL

		Dim ret As Boolean

		' 読み取りオブジェクトが閉じていない場合は、閉じる
		If Not Me.myReader Is Nothing Then
			If Not Me.myReader.IsClosed Then
				Me.myReader.Close()
			End If
		End If

		Me.myCommand.CommandText = SQL

		Try
			Me.myReader = myCommand.ExecuteReader()
			ret = True
		Catch ex As Exception
			Me._myError = ex.Message
			ret = False
		End Try

		Return ret

	End Function

	' ******************************************************
	' 1行読み込む
	' ※ データが無くなると False を返す
	' ******************************************************
	Public Function Read() As Boolean _
	 Implements DbInterface.Read

		If Not Me.myReader Is Nothing Then
			If Not Me.myReader.IsClosed Then
				Return Me.myReader.Read()
			Else
				Me._myError = "Reader は閉じられています"
				Return False
			End If
		Else
			Me._myError = "Query が一度も実行されていません"
			Return False
		End If

	End Function

	' ******************************************************
	' SQL を実行して1行読み込む
	' ******************************************************
	Public Function QueryAndRead(ByVal SQL As String) As Boolean _
	 Implements DbInterface.QueryAndRead

		Dim ret As Boolean

		ret = Me.Query(SQL)
		If ret Then
			ret = Me.Read()
		End If

		Return ret

	End Function

	' ******************************************************
	' UPDATE、INSERT、および DELETE を実行する
	' 戻り値は影響を受けた行数
	' -1 は他の SQL を実行した場合
	' -2 はエラー
	' ******************************************************
	Public Function Execute(ByVal SQL As String) As Integer _
	 Implements DbInterface.Execute

		Me._SqlString = SQL

		Dim ret As Integer
		Dim execCommand As OleDbCommand = New OleDbCommand()

		execCommand.CommandText = SQL
		execCommand.Connection = Me.myCon
		Try
			ret = execCommand.ExecuteNonQuery()
		Catch ex As Exception
			ret = -2
			Me._myError = ex.Message
		End Try
		execCommand.Dispose()

		Return ret

	End Function

	' ******************************************************
	' 指定した列名より文字列として値を得る
	' ******************************************************
	Public Function GetValue(ByVal ColumnName As String) As String _
	 Implements DbInterface.GetValue

		Dim ret As String = ""
		Dim fld As Integer = 0

		fld = Me.myReader.GetOrdinal(ColumnName)
		If Me.myReader.IsDBNull(fld) Then
			ret = ""
		Else
			ret = Me.myReader.GetValue(fld).ToString()
		End If

		Return ret
	End Function

	' ******************************************************
	' 日付時間型として、日付部分を文字列として値を得る
	' ******************************************************
	Public Function GetDate(ByVal ColumnName As String) As String _
	 Implements DbInterface.GetDate

		Dim ret As String = ""
		Dim fld As Integer = 0

		fld = Me.myReader.GetOrdinal(ColumnName)
		If Me.myReader.IsDBNull(fld) Then
			ret = ""
		Else
			Try
				ret = Me.myReader.GetDateTime(fld).ToString("d")
			Catch ex As Exception
				ret = ""
				Me._myError = ex.Message
			End Try
		End If

		Return ret
	End Function

	' ******************************************************
	' 接続解除
	' ******************************************************
	Public Sub Close() _
	 Implements DbInterface.Close

		' 読み取りオブジェクトが閉じていない場合は、閉じる
		If Not Me.myReader Is Nothing Then
			If Not Me.myReader.IsClosed Then
				Me.myReader.Close()
			End If
		End If

		If Not Me.myCon Is Nothing Then
			' 接続を閉じる
			Me.myCon.Close()

			' リソースの開放
			Me.myCon.Dispose()
			Me.myCommand.Dispose()

			' 次に備えて初期化
			Me.myCon = Nothing
		End If

	End Sub

End Class

' ******************************************************
' SQLServer
' ******************************************************
Public Class DbSql
	Implements DbInterface

	' ******************************************************
	' 内部変数( プロパティ )
	' ※ Public は、開発中なので都合がいいように
	' ******************************************************
	Public _myConnectString As String = Nothing
	Public myCon As SqlConnection = Nothing
	Public myCommand As SqlCommand = New SqlCommand()
	Public myReader As SqlDataReader = Nothing
	Public _myError As String = ""
	Public _SqlString As String = ""

	Public ReadOnly Property myConnectString() As String _
	  Implements DbInterface.myConnectString
		Get
			Return _myConnectString
		End Get
	End Property

	Public ReadOnly Property myError() As String _
	  Implements DbInterface.myError
		Get
			Return _myError
		End Get
	End Property

	Public ReadOnly Property SqlString() As String _
	  Implements DbInterface.SqlString
		Get
			Return _SqlString
		End Get
	End Property

	' ******************************************************
	' コンストラクタ
	' ******************************************************
	Public Sub New( _
	 ByVal sv As String, _
	 ByVal db As String, _
	 ByVal user As String, _
	 ByVal pass As String)

		Me._myConnectString = _
		 "Data Source=" + sv + ";" + _
		 "Initial Catalog=" + db + ";" + _
		 "User ID=" + user + ";" + _
		 "Password=" + pass + ";"

	End Sub

	' ******************************************************
	' 接続
	' ******************************************************
	Public Function Connect() As Boolean _
	 Implements DbInterface.Connect

		Dim ret As Boolean

		Me.myCon = New SqlConnection()
		Me.myCon.ConnectionString = Me.myConnectString

		Try
			Me.myCon.Open()
			Me.myCommand.Connection = Me.myCon
			ret = True
		Catch ex As Exception
			Me.myCon = Nothing
			Me._myError = "接続エラーです" + ControlChars.CrLf
			Me._myError += "接続文字列=" + Me.myConnectString + ControlChars.CrLf
			Me._myError += "システムのメッセージ=" + ex.Message + ControlChars.CrLf
			ret = False
		End Try

		Return ret

	End Function

	' ******************************************************
	' SQL を実行して読み込みの準備
	' ※ OleDbDataReader を作成
	' ******************************************************
	Public Function Query(ByVal SQL As String) As Boolean _
	 Implements DbInterface.Query

		Me._SqlString = SQL

		Dim ret As Boolean

		' 読み取りオブジェクトが閉じていない場合は、閉じる
		If Not Me.myReader Is Nothing Then
			If Not Me.myReader.IsClosed Then
				Me.myReader.Close()
			End If
		End If

		Me.myCommand.CommandText = SQL

		Try
			Me.myReader = myCommand.ExecuteReader()
			ret = True
		Catch ex As Exception
			Me._myError = ex.Message
			ret = False
		End Try

		Return ret

	End Function

	' ******************************************************
	' 1行読み込む
	' ※ データが無くなると False を返す
	' ******************************************************
	Public Function Read() As Boolean _
	 Implements DbInterface.Read

		If Not Me.myReader Is Nothing Then
			If Not Me.myReader.IsClosed Then
				Return Me.myReader.Read()
			Else
				Me._myError = "Reader は閉じられています"
				Return False
			End If
		Else
			Me._myError = "Query が一度も実行されていません"
			Return False
		End If

	End Function

	' ******************************************************
	' SQL を実行して1行読み込む
	' ******************************************************
	Public Function QueryAndRead(ByVal SQL As String) As Boolean _
	 Implements DbInterface.QueryAndRead

		Dim ret As Boolean

		ret = Me.Query(SQL)
		If ret Then
			ret = Me.Read()
		End If

		Return ret

	End Function

	' ******************************************************
	' UPDATE、INSERT、および DELETE を実行する
	' 戻り値は影響を受けた行数
	' -1 は他の SQL を実行した場合
	' -2 はエラー
	' ******************************************************
	Public Function Execute(ByVal SQL As String) As Integer _
	 Implements DbInterface.Execute

		Me._SqlString = SQL

		Dim ret As Integer
		Dim execCommand As SqlCommand = New SqlCommand()

		execCommand.CommandText = SQL
		execCommand.Connection = Me.myCon
		Try
			ret = execCommand.ExecuteNonQuery()
		Catch ex As Exception
			ret = -2
			Me._myError = ex.Message
		End Try
		execCommand.Dispose()

		Return ret

	End Function

	' ******************************************************
	' 指定した列名より文字列として値を得る
	' ******************************************************
	Public Function GetValue(ByVal ColumnName As String) As String _
	 Implements DbInterface.GetValue
		Dim ret As String = ""
		Dim fld As Integer = 0

		fld = Me.myReader.GetOrdinal(ColumnName)
		If Me.myReader.IsDBNull(fld) Then
			ret = ""
		Else
			ret = Me.myReader.GetValue(fld).ToString()
		End If

		Return ret
	End Function

	' ******************************************************
	' 日付時間型として、日付部分を文字列として値を得る
	' ******************************************************
	Public Function GetDate(ByVal ColumnName As String) As String _
	 Implements DbInterface.GetDate
		Dim ret As String = ""
		Dim fld As Integer = 0

		fld = Me.myReader.GetOrdinal(ColumnName)
		If Me.myReader.IsDBNull(fld) Then
			ret = ""
		Else
			Try
				ret = Me.myReader.GetDateTime(fld).ToString("d")
			Catch ex As Exception
				ret = ""
				Me._myError = ex.Message
			End Try
		End If

		Return ret
	End Function

	' ******************************************************
	' 接続解除
	' ******************************************************
	Public Sub Close() _
	 Implements DbInterface.Close

		' 読み取りオブジェクトが閉じていない場合は、閉じる
		If Not Me.myReader Is Nothing Then
			If Not Me.myReader.IsClosed Then
				Me.myReader.Close()
			End If
		End If

		If Not Me.myCon Is Nothing Then
			' 接続を閉じる
			Me.myCon.Close()

			' リソースの開放
			Me.myCon.Dispose()
			Me.myCommand.Dispose()

			' 次に備えて初期化
			Me.myCon = Nothing
		End If

	End Sub

End Class

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