DataTable: schnelle Erstellung eines DataRow-Objekts

Sprache: VB

Manchmal benötigt man schnell eine Daten-Klasse (DataFactory), die eine Zeile einer DataTable zurückgibt. Natürlich mit schnellem Austausch der Daten gegenseitig und komfortablen Zugriff auf die Daten per Feldnamen. Vorgehensweise: 1. Einmalig eine abstrakte Klasse erstellen, immer wieder verwendbar (hier: DataClass(Of T)). 2. Datenfeldnamen einer Tabelle in einer Enumerations festlegen. 3. Erstellung der Datenklasse (6 Zeilen) mit Inherits DataClass und Verweis auf die Eunumeration.

'	Erstellen der abstrakten Klasse
<Serializable()> Public MustInherit Class DataClass(Of T)
        Implements IDisposable

        Private Values As Dictionary(Of T, Object)
        Private Columns As List(Of T)
        Private m_ErrMsgDataRow As String = ""

        Public Sub New()
            Values = New Dictionary(Of T, Object)
            Columns = New List(Of T)
            Columns.AddRange(CType([Enum].GetValues(GetType(T)), _
                             Global.System.Collections.Generic.IEnumerable(Of T)))
        End Sub

        ''' <summary>
        ''' Anzahl der Felder, die Datenwerte enthalten können
        ''' </summary>
        ''' <value></value>
        ''' <returns></returns>
        ''' <remarks></remarks>
        ReadOnly Property Fields() As List(Of T)
            Get
                Return Columns
            End Get
        End Property

        ''' <summary>
        ''' Anzahl der Datenwerte
        ''' </summary>
        ''' <value></value>
        ''' <returns></returns>
        ''' <remarks></remarks>
        ReadOnly Property CountValues() As Integer
            Get
                Return Values.Count
            End Get
        End Property

        ''' <summary>
        ''' überprüft ob alle Datenfelder einen Wert haben
        ''' </summary>
        ''' <value></value>
        ''' <returns></returns>
        ''' <remarks></remarks>
        ReadOnly Property HasAllFieldsDatas() As Boolean
            Get
                Return CBool(Values.Count = Columns.Count)
            End Get
        End Property

        ''' <summary>
        ''' Gibt den Wert eines Elements zurück
        ''' </summary>
        ''' <param name="e"></param>
        ''' <returns></returns>
        ''' <remarks></remarks>
        Public Function GetItem(ByVal e As T) As Object
            Try
                If Me.Values(e) Is Nothing Then Me.Values(e) = ""
                Return Me.Values(e)
            Catch : End Try
            Return Nothing
        End Function

        ''' <summary>
        ''' Setzt den Wert eines Elements
        ''' </summary>
        ''' <param name="Value"></param>
        ''' <param name="e"></param>
        ''' <remarks></remarks>
        Public Sub SetItem(ByVal e As T, ByVal Value As Object)
            Me.Values(e) = Value
        End Sub

        ''' <summary>
        ''' Setzt die Daten einer Zeile in die Klasse um
        ''' </summary>
        ''' <param name="row"></param>
        ''' <remarks></remarks>
        Public Sub Fill_Class(ByVal row As DataRow)
            m_ErrMsgDataRow = ""
            If row IsNot Nothing Then
                For Each p As T In Columns
                    Try
                        SetItem(p, row(p.ToString))
                    Catch ex As Exception
                        m_ErrMsgDataRow += ex.Message + ControlChars.NewLine
                    End Try
                Next
                Exit Sub
            End If
            m_ErrMsgDataRow = "Datenobjekt ist Nothing."
        End Sub

        ''' <summary>
        ''' Liest die Variablen in das DataRow ein
        ''' </summary>
        ''' <param name="row"></param>
        ''' <remarks></remarks>
        Public Sub Fill_DataRow(ByVal row As DataRow, Optional ByVal AndAddToTable As Boolean = False)
            m_ErrMsgDataRow = ""
            If row IsNot Nothing Then
                For Each p As T In Columns
                    Try
                        row(p.ToString) = GetItem(p)
                    Catch ex As Exception
                        m_ErrMsgDataRow += ex.Message + ControlChars.NewLine
                    End Try
                Next
                If AndAddToTable Then row.Table.Rows.Add(row)
                Exit Sub
            End If
            m_ErrMsgDataRow = "Datenobjekt ist Nothing."
        End Sub

        ''' <summary>
        ''' Gibt die Fehler zurück, die im Zusammenhang mit
        ''' einen DataRow-Objekt entstanden sind.
        ''' </summary>
        ''' <value></value>
        ''' <returns></returns>
        ''' <remarks></remarks>
        ReadOnly Property ErrMsgFromDataRow() As String
            Get
                Return m_ErrMsgDataRow
            End Get
        End Property

#Region " IDisposable Support "
        Private disposedValue As Boolean = False        
        Protected Overridable Sub Dispose(ByVal disposing As Boolean)
            If Not Me.disposedValue Then
                If disposing Then
                    Values = Nothing: Columns = Nothing
                End If
                ' TODO: free your own state (unmanaged objects).
                ' TODO: set large fields to null.
            End If
            Me.disposedValue = True
        End Sub
        ' This code added by Visual Basic to correctly implement the disposable pattern.
        Public Sub Dispose() Implements IDisposable.Dispose
            ' Do not change this code.  Put cleanup code in Dispose(ByVal disposing As Boolean) above.
            Dispose(True)
            GC.SuppressFinalize(Me)
        End Sub
#End Region
    
End Class

'	Datenfeldnamen festlegen
Public Enum FieldsKontoInfo
        ID
        KontoNr
        Blz
        Bank
        Bez
        Inhaber
        Iban
        Swift
        DatumGesperrtAb
        DatumErstelltAm
        BetragStart
End Enum

'	Erstellung der Datenklasse
'	mit komfortablem Zugriff auf die Daten per Feldnamen
Public Class ClsKontoInfo
        Inherits DataClass(Of FieldsKontoInfo)

        Public Sub New()
            MyBase.New()
        End Sub
End Class

'	Erstellen der abstrakten Klasse
<Serializable()> Public MustInherit Class DataClass(Of T)
        Implements IDisposable

        Private Values As Dictionary(Of T, Object)
        Private Columns As List(Of T)
        Private m_ErrMsgDataRow As String = ""

        Public Sub New()
            Values = New Dictionary(Of T, Object)
            Columns = New List(Of T)
            Columns.AddRange(CType([Enum].GetValues(GetType(T)), _
                             Global.System.Collections.Generic.IEnumerable(Of T)))
        End Sub

        ''' <summary>
        ''' Anzahl der Felder, die Datenwerte enthalten können
        ''' </summary>
        ''' <value></value>
        ''' <returns></returns>
        ''' <remarks></remarks>
        ReadOnly Property Fields() As List(Of T)
            Get
                Return Columns
            End Get
        End Property

        ''' <summary>
        ''' Anzahl der Datenwerte
        ''' </summary>
        ''' <value></value>
        ''' <returns></returns>
        ''' <remarks></remarks>
        ReadOnly Property CountValues() As Integer
            Get
                Return Values.Count
            End Get
        End Property

        ''' <summary>
        ''' überprüft ob alle Datenfelder einen Wert haben
        ''' </summary>
        ''' <value></value>
        ''' <returns></returns>
        ''' <remarks></remarks>
        ReadOnly Property HasAllFieldsDatas() As Boolean
            Get
                Return CBool(Values.Count = Columns.Count)
            End Get
        End Property

        ''' <summary>
        ''' Gibt den Wert eines Elements zurück
        ''' </summary>
        ''' <param name="e"></param>
        ''' <returns></returns>
        ''' <remarks></remarks>
        Public Function GetItem(ByVal e As T) As Object
            Try
                If Me.Values(e) Is Nothing Then Me.Values(e) = ""
                Return Me.Values(e)
            Catch : End Try
            Return Nothing
        End Function

        ''' <summary>
        ''' Setzt den Wert eines Elements
        ''' </summary>
        ''' <param name="Value"></param>
        ''' <param name="e"></param>
        ''' <remarks></remarks>
        Public Sub SetItem(ByVal e As T, ByVal Value As Object)
            Me.Values(e) = Value
        End Sub

        ''' <summary>
        ''' Setzt die Daten einer Zeile in die Klasse um
        ''' </summary>
        ''' <param name="row"></param>
        ''' <remarks></remarks>
        Public Sub Fill_Class(ByVal row As DataRow)
            m_ErrMsgDataRow = ""
            If row IsNot Nothing Then
                For Each p As T In Columns
                    Try
                        SetItem(p, row(p.ToString))
                    Catch ex As Exception
                        m_ErrMsgDataRow += ex.Message + ControlChars.NewLine
                    End Try
                Next
                Exit Sub
            End If
            m_ErrMsgDataRow = "Datenobjekt ist Nothing."
        End Sub

        ''' <summary>
        ''' Liest die Variablen in das DataRow ein
        ''' </summary>
        ''' <param name="row"></param>
        ''' <remarks></remarks>
        Public Sub Fill_DataRow(ByVal row As DataRow, Optional ByVal AndAddToTable As Boolean = False)
            m_ErrMsgDataRow = ""
            If row IsNot Nothing Then
                For Each p As T In Columns
                    Try
                        row(p.ToString) = GetItem(p)
                    Catch ex As Exception
                        m_ErrMsgDataRow += ex.Message + ControlChars.NewLine
                    End Try
                Next
                If AndAddToTable Then row.Table.Rows.Add(row)
                Exit Sub
            End If
            m_ErrMsgDataRow = "Datenobjekt ist Nothing."
        End Sub

        ''' <summary>
        ''' Gibt die Fehler zurück, die im Zusammenhang mit
        ''' einen DataRow-Objekt entstanden sind.
        ''' </summary>
        ''' <value></value>
        ''' <returns></returns>
        ''' <remarks></remarks>
        ReadOnly Property ErrMsgFromDataRow() As String
            Get
                Return m_ErrMsgDataRow
            End Get
        End Property

#Region " IDisposable Support "
        Private disposedValue As Boolean = False        
        Protected Overridable Sub Dispose(ByVal disposing As Boolean)
            If Not Me.disposedValue Then
                If disposing Then
                    Values = Nothing: Columns = Nothing
                End If
                ' TODO: free your own state (unmanaged objects).
                ' TODO: set large fields to null.
            End If
            Me.disposedValue = True
        End Sub
        ' This code added by Visual Basic to correctly implement the disposable pattern.
        Public Sub Dispose() Implements IDisposable.Dispose
            ' Do not change this code.  Put cleanup code in Dispose(ByVal disposing As Boolean) above.
            Dispose(True)
            GC.SuppressFinalize(Me)
        End Sub
#End Region
    
End Class

'	Datenfeldnamen festlegen
Public Enum FieldsKontoInfo
        ID
        KontoNr
        Blz
        Bank
        Bez
        Inhaber
        Iban
        Swift
        DatumGesperrtAb
        DatumErstelltAm
        BetragStart
End Enum

'	Erstellung der Datenklasse
'	mit komfortablem Zugriff auf die Daten per Feldnamen
Public Class ClsKontoInfo
        Inherits DataClass(Of FieldsKontoInfo)

        Public Sub New()
            MyBase.New()
        End Sub
End Class

Abgelegt unter DataFactory DataRow DataTable Enum Objekte

Alte URL: /snippet/datatable-schnelle-erstellung-eines-datarow-objekts/771