how to fix null error with regex.match.group.value

Question

Friend Sub DetectBaseUrl()

Dim domain As String = Nothing

Dim match As String = Regex.Match(GmailClient.Username, ".+@(.+)").Groups(1).Value

If match = String.Empty AndAlso Not New String() {"gmail.com", "googlemail.com", "googlemail.co.uk"}.Contains(match) Then

domain = match

End If

BaseUrl = "http://mail.google.com" + (If((domain IsNot Nothing), ("/a/" + domain), Nothing))

End Sub