Le développeurs ont pris l’habitude de manipuler les données à l’aide de Dataset et de DataTable. Depuis l’arrivé de LINQ leurs habitudes ont un peu changé et ils ont du s’habituer à travailler plus souvent avec des IEnumerable(of Anonyme).
La méthode CopyToDatatable permet de copier les résultats d’une requête LINQ dans un DataTable.
Cette méthode est très pratique si l’on veut continuer de travailler avec des DataTables. Le problème c’est que cette méthode n’est disponible que si le résultat de votre requête LINQ est de type DataRow.
Pour pouvoir utiliser CopyToDataTable pour d’autres types, vous devez ajouter le code suivant à votre application.
Code :
Imports System.Reflection
Public Class ObjectShredder(Of T)
Private _fi As FieldInfo()
Private _ordinalMap As Dictionary(Of String, Integer)
Private _pi As PropertyInfo()
Private _type As Type
Public Sub New()
Me._type = GetType(T)
Me._fi = Me._type.GetFields
Me._pi = Me._type.GetProperties
Me._ordinalMap = New Dictionary(Of String, Integer)
End Sub
Public Function ShredObject(ByVal table As DataTable, ByVal instance As T) As Object()
Dim fi As FieldInfo() = Me._fi
Dim pi As PropertyInfo() = Me._pi
If (Not instance.GetType Is GetType(T)) Then
' Si l'instance dérive de T, étendre le schéma de la table
' et récupérer les propirétés et les champs
Me.ExtendTable(table, instance.GetType)
fi = instance.GetType.GetFields
pi = instance.GetType.GetProperties
End If
' Add the property and field values of the instance to an array.
Dim values As Object() = New Object(table.Columns.Count - 1) {}
Dim f As FieldInfo
For Each f In fi
values(Me._ordinalMap.Item(f.Name)) = f.GetValue(instance)
Next
Dim p As PropertyInfo
For Each p In pi
values(Me._ordinalMap.Item(p.Name)) = p.GetValue(instance, Nothing)
Next
' Return the property and field values of the instance.
Return values
End Function
' Summary: Loads a DataTable from a sequence of objects.
' source parameter: The sequence of objects to load into the DataTable.</param>
' table parameter: The input table. The schema of the table must match that
' the type T. If the table is null, a new table is created
' with a schema created from the public properties and fields
' of the type T.
' options parameter: Specifies how values from the source sequence will be applied to
' existing rows in the table.
' Returns: A DataTable created from the source sequence.
Public Function Shred(ByVal source As IEnumerable(Of T), ByVal table As DataTable, ByVal options As LoadOption?) As DataTable
' Load the table from the scalar sequence if T is a primitive type.
If GetType(T).IsPrimitive Then
Return Me.ShredPrimitive(source, table, options)
End If
' Create a new table if the input table is null.
If (table Is Nothing) Then
table = New DataTable(GetType(T).Name)
End If
' Initialize the ordinal map and extend the table schema based on type T.
table = Me.ExtendTable(table, GetType(T))
' Enumerate the source sequence and load the object values into rows.
table.BeginLoadData()
Using e As IEnumerator(Of T) = source.GetEnumerator
Do While e.MoveNext
If options.HasValue Then
table.LoadDataRow(Me.ShredObject(table, e.Current), options.Value)
Else
table.LoadDataRow(Me.ShredObject(table, e.Current), True)
End If
Loop
End Using
table.EndLoadData()
' Return the table.
Return table
End Function
Public Function ShredPrimitive(ByVal source As IEnumerable(Of T), ByVal table As DataTable, ByVal options As LoadOption?) As DataTable
' Create a new table if the input table is null.
If (table Is Nothing) Then
table = New DataTable(GetType(T).Name)
End If
If Not table.Columns.Contains("Value") Then
table.Columns.Add("Value", GetType(T))
End If
' Enumerate the source sequence and load the scalar values into rows.
table.BeginLoadData()
Using e As IEnumerator(Of T) = source.GetEnumerator
Dim values As Object() = New Object(table.Columns.Count - 1) {}
Do While e.MoveNext
values(table.Columns.Item("Value").Ordinal) = e.Current
If options.HasValue Then
table.LoadDataRow(values, options.Value)
Else
table.LoadDataRow(values, True)
End If
Loop
End Using
table.EndLoadData()
' Return the table.
Return table
End Function
Public Function ExtendTable(ByVal table As DataTable, ByVal type As Type) As DataTable
' Extend the table schema if the input table was null or if the value
' in the sequence is derived from type T.
Dim f As FieldInfo
Dim p As PropertyInfo
For Each f In type.GetFields
If Not Me._ordinalMap.ContainsKey(f.Name) Then
Dim dc As DataColumn
' Add the field as a column in the table if it doesn't exist
' already.
dc = IIf(table.Columns.Contains(f.Name), table.Columns.Item(f.Name), table.Columns.Add(f.Name, f.FieldType))
' Add the field to the ordinal map.
Me._ordinalMap.Add(f.Name, dc.Ordinal)
End If
Next
For Each p In type.GetProperties
If Not Me._ordinalMap.ContainsKey(p.Name) Then
' Add the property as a column in the table if it doesn't exist
' already.
Dim dc As DataColumn
dc = IIf(table.Columns.Contains(p.Name), table.Columns.Item(p.Name), table.Columns.Add(p.Name, p.PropertyType))
' Add the property to the ordinal map.
Me._ordinalMap.Add(p.Name, dc.Ordinal)
End If
Next
' Return the table.
Return table
End Function
End Class
