Удаление дубликатов

 Dim iplist As New List(Of String)
        Dim outlist As New List(Of String)
        Dim goodlist As New List(Of String)
        Dim badlist As New List(Of String)
        Dim max_dubl As Integer = 3
        Dim ip as string
        Dim port as string
 
        For Each line As String In File.ReadLines("IPs.txt")
            Dim seperator() As String = {":"}
            Dim part As String() = line.Split(seperator, StringSplitOptions.RemoveEmptyEntries)
 
            ip = part(0)
            port = part(1)
 
            iplist.Add(ip)
            outlist.Add(line)
        Next
 
        For Each item In outlist
            Dim seperator() As String = {":"}
            Dim part As String() = item.Split(seperator, StringSplitOptions.RemoveEmptyEntries)
 
            If iplist.Where(Function(value) value = part(0)).Count <= max_dubl Then
 
                goodlist.Add(item)
 
            Else
 
                badlist.Add(item)
 
            End If
        Next
 
        System.IO.File.WriteAllLines("Good.txt", goodlist)  
        System.IO.File.WriteAllLines("Bad.txt", badlist)

Dim goodList As List(Of String) = File.ReadLines("IPs.txt").
    GroupBy(Function(l) l.Split(":"c)(0)).
    Select(Function(g) If(g.Count() < 4, g, g.Take(1))).
    SelectMany(Function(g) g).
    ToList()

If iplist.Where(Function(value) value = part(0)).Count <= max_dubl Then
                goodlist.Add(item)
            Else
                badlist.Add(item)
            End If