how can I get an undupliated count

I need to get an unduplicated count of the emails in my results. Does anyone have any ideas on how this could be done?
' search for email addresses Dim i As Integer = 0 Dim intCount As Integer = 0 Dim emails As String() Dim email As String Dim results As New StringBuilder emails = ExtractEmailAddressesFromString(contents) For Each email In emails intCount += 1 results.Append(email & vbNewLine) Next     Private Function ExtractEmailAddressesFromString(ByVal source As String) _
        As String()
        Dim mc As MatchCollection
        Dim i As Integer

      & ...