Private Function Wortliste(ByVal filename As String) As List(Of String)
   If Not System.IO.File.Exists(filename) Then Return Nothing
 
   Dim lst As New List(Of String)
   Dim sep(0) As String
   Dim enc As New System.Text.UTF8Encoding
 
   sep(0) = vbCrLf
   Dim t As String = My.Computer.FileSystem.ReadAllText(filename, enc)
   Dim l() As String = t.Split(sep, StringSplitOptions.RemoveEmptyEntries)
   For Each line As String In l
       Dim w() As String = line.Split(" "c)
       For i As Integer = 0 To w.Length - 1
          w(i) = _
          w(i).Trim("("c, ")"c, ","c, ";"c, "."c, "-"c, "?"c, "!"c, "/"c, _
          "\"c).ToUpper
       Next i
       lst.AddRange(w)
   Next line
 
   lst.RemoveAll(AddressOf IsNullOrShort)
   lst.Sort()
   Return lst
End Function
 
Private Function IsNullOrShort(ByVal str As String) As Boolean
   If String.IsNullOrWhiteSpace(str) Then Return True
   If str.Length < 4 Then Return True
   Return False
End Function

Dim worte As List(Of String) = Wortliste("Datei mit Liste häufiger Worte")
 
Dim abschnitte As List(Of String) = Wortliste("zu prüfende Datei")
 
Dim sum As Integer = 0
For Each abschnitt As String In abschnitte
   If worte.BinarySearch(abschnitt) > -1 Then sum += 1
Next abschnitt
Dim wortprozente As Double = sum / abschnitte.Count * 100.0#