VB.Net List Distinct and ToList methods not recognized by the compiler.

Question

User2023521679 posted

I have a function that takes a input string of e-mail addresses which could be separated by various characters and may contain duplicates. My function sorts, removed duplicates and returns a comma delimited list. This works great in two web applications that I have. I tried adding similar code to a windows forms application and it doesn't recognize the .Distinct method or the .ToList. I am targeting .net framework 4.0 in my compile tab. Please advise.

   Function SplitSortRemoveDuplicates(ByVal InputString As String, Optional ByVal ListSeparator As String = ", ") As String
      Dim EMailAddressListSplitCharacters As Char() = {CChar(" "), CChar(","), CChar(";"), Chr(10)}
      Dim StringList As List(Of String) = InputString.Split(EMailAddressListSplitCharacters, StringSplitOptions.RemoveEmptyEntries).Distinct(StringComparer.InvariantCultureIgnoreCase).ToList

      StringList.Sort(StringComparer.InvariantCultureIgnoreCase)

      Return String.Join(ListSeparator, StringList)
   End Function