Ho gestito una listview con raggruppamenti (più di uno).
Volevo riportare il totale ma, scopiazzando di qua e di la, non riesco a farlo.
Ho utilizzato una interfaccia IValueConverter, ma quando vado a dichiarare var mi da questo errore:

"Unable to cast object of type 'MS.Internal.Data.CollectionViewGroupInternal' to type
'MiaClasse'."}
riporto il converter

Imports System.Collections.ObjectModel

Public Class myConverter


Implements IValueConverter

Public Function Convert(ByVal value As Object, ByVal targetType As Type, ByVal parameter As Object, ByVal culture As System.Globalization.CultureInfo) As Object _
Implements IValueConverter.Convert

Dim items As ReadOnlyObservableCollection(Of Object) = CType(value, Global.System.Collections.ObjectModel.ReadOnlyObse rvableCollection(Of Object))
Dim var As Integer = (From i In items Select (CType(i,MiaClasse).Importo)).Sum

Return var.ToString()
End Function


Public Function ConvertBack(ByVal value As Object, ByVal targetType As Type, _
ByVal parameter As Object, _
ByVal culture As System.Globalization.CultureInfo) As Object _
Implements IValueConverter.ConvertBack
Throw New NotImplementedException()
End Function



End Class