'Dateiinhalte in Listen eintragen
Dim lst1 As System.Collections.Generic.List(Of String) = _
    System.IO.File.ReadAllLines(filename1).ToList
 
Dim lst2 As System.Collections.Generic.List(Of String) = _
    System.IO.File.ReadAllLines(filename2).ToList
 
Dim In1AberNichtIn2 As New List(Of String)
 
'Listeneinträge vergleichen
For index As Integer = 0 To lst1.Count - 1
   If Not lst2.Contains(lst1(index)) Then 
     In1AberNichtIn2.Add(lst1(index))
   End If
Next index