Private Class SubstringComparer
        Implements System.Collections.Generic.IComparer(Of String)
 
        Dim _splitchar As Char
        Dim _blockindex As Integer
 
        Public Sub New(SplitChar As Char, Blockindex As Integer)
            _splitchar = SplitChar
            _blockindex = Blockindex
        End Sub
 
        Public Function Compare(x As String, y As String) As Integer _
            Implements System.Collections.Generic.IComparer(Of String).Compare
 
            Dim x1 As String = x.Split(_splitchar)(_blockindex)
            Dim y1 As String = y.Split(_splitchar)(_blockindex)
 
            Return x1.CompareTo(y1)
        End Function
    End Class

  Dim lines() As String = IO.File.ReadAllLines("C:\daten\times.txt")
 
  Array.Sort(lines, New SubstringComparer(" "c, 1))
 
  IO.File.WriteAllLines("C:\daten\times_sort.txt", lines)