public static TimeSpan Days(this int input) { return TimeSpan.FromDays(input); }

public static DateTime Ago(this TimeSpan input) { return (DateTime.Now - input); }

DateTime when = 24.Days().Ago();

List <(new { Word = "", Instances = 0 }).GetType()> words2 =
  new List<(new { Word = "", Instances = 0 }).GetType()>();

private static List<string> ComplexDuplicateFilter(List<string> input)
{
 if (input == null || input.Count == 0)
  return input;
 input = input.Distinct().ToList();

 // Build a list of words and how many times they occur in the overall list
 List<dynamic> words2 = new List<dynamic>();
 foreach (string line in input)
  foreach (string word in line.Split(new char[] { ' ', ',', ';', '\\', '/', ':', '\r', '\n' }))
  {
   if (string.IsNullOrEmpty(word))
    continue;
   else if (ExistsInList(word, words2))
   foreach (dynamic dyn in words2)
    {
     if (dyn.Word == word)
      dyn.Instances++;
    }
   else words2.Add(new { Word = word, Instances = 0 });
  }

// Remove extraneous entries for common word permutations
 List<string> output = new List<string>();
 foreach (dynamic dyn in words2)
  if ((dyn.Iterations > 5 && !output.Contains(dyn.Word)) ||
   dyn.Iterations <= 5)
    output.Add(dyn.Word);

 return output;
}

private static bool ExistsInList(string word, List<dynamic> words)
{
 foreach (dynamic dyn in words)
  if (dyn.Word == word)
   return true;
 return false;
}

  private static List<string> FilterByDuplicateWords(List<string> input)
  {
   if (input == null || input.Count == 0)
    return input;
   input = input.Distinct().ToList();

   // Build a list of words and how many times they occur in the overall list
   List<dynamic> words2 = new List<object>();
   foreach (string line in input)
    foreach (string word in line.Split(new char[] { ' ', ',', ';', '\\', '/', ':', '\"', '\r', '\n', '.' }))
    {
     if (string.IsNullOrEmpty(word))
      continue;
     else if (ExistsInList(word, words2))
      for (int i=words2.Count - 1; i >= 0; i--)
      {
       if (words2[i].Word == word)
        words2[i] = new { Word = words2[i].Word, Instances = words2[i].Instances + 1};
      }
     else words2.Add(new { Word = word, Instances = 1 });
    }

   // Remove extraneous entries for common word permutations
   List<string> output = new List<string>();
   foreach (string line in input)
   {
    int Dupes = 0;
    foreach (string word in line.Split(new char[] { ' ', ',', ';', '\\', '/', ':', '\"', '\r', '\n', '.' })
     .Where(p => p.Length > 7)
     .Distinct())
    {
     int Instances = 0;
     foreach (dynamic dyn in words2)
      if (word == dyn.Word)
      {
       Instances = dyn.Instances;
       if (Instances > 1)
        Dupes++;
       break;
      }
    }
    if (Dupes == 0)
     output.Add(line);
   }
   return output;
  }

  private static bool ExistsInList(string word, List<dynamic> words)
  {
   foreach (dynamic dyn in words)
    if (dyn.Word == word)
     return true;
   return false;
  }