Auto hyperlink URL and also format BBCode tags.

I have some text. User can type:

http://www.asp.net
and I'm activating this non-hyperlink text by the code below:
[Kod VisualBasic]
      Public Shared Function ActivateWebSiteUrl(ByVal siteString As String) As String
        Dim buf As String = siteString
        Dim patternSite As String = "http(s)?://([\w-]+\.)+[\w-]+(/[\w\d:#@%/;$()~_?\+-=\\\.&]*)?"
        Dim re As Regex = New Regex(patternSite)
        If re.IsMatch(buf) Then
            buf = re.Replace(buf, AddressOf WebSiteMatchEvaluator)
        End If
 & ...