Concept needed for building consistent urls (routes) - asp.net

Question

My project has the need to build consistent urls similar to the ones here on stackoverflow. I know how I "can" do it by running the string through multiple filters, but I'm wondering if I can do it all with a single method.
Basically I want to remove all special characters, and replace them with dashes BUT if there are multiple dashes in a row, I need them to be a single dash. How can I implement this as clean as possible?
Example: If I were to use the following string.
My #1 Event
My regex would create the following string
my--1-event
notice how there are two dashes (one for the space and one for the "#" symbol). What I need is
my-1-event
Here's how I'm implementing it currently
''# <System.Runtime.CompilerServices.Extension()>
Public Function ToUrlFriendlyString(ByVal input As String) As String
Dim reg As New Regex("[^A-Za-z0-9]")
''# I could run a loop filter here to match "--" and replace it with "-"
''# but that seems like more overhead than necessary.
Return (reg.Replace(Trim(input), "-"))
End Function
And then all I do is call the extension method
Dim UrlFriendlyString = MyTile.ToUrlFriendlyString
Thanks in advance.

Answer 1

Add a + to the end of the regex.
This will tell it to match one or more characters that match the character class that precedes the +.
Also, you should create your Regex instance in a Shared field outside the method so that .Net won't need to parse the regex again every time you call the method.
[edited by rockinthesixstring]: here's the final result
Private UrlRegex As Regex = New Regex("[^a-z0-9]+", RegexOptions.IgnoreCase)
<System.Runtime.CompilerServices.Extension()>
Public Function ToUrlFriendlyString(ByVal input As String) As String
Return (UrlRegex.Replace(Trim(input), "-"))
End Function

Answer 2

Another way I do this without using a regex and also is a little simpler to understand is the following:
Excuse me on my vb as I am mainly C# guy.
''# <System.Runtime.CompilerServices.Extension()>
Public Function ToUrlFriendlyString(ByVal input As String) As String
If [String].IsNullOrEmpty(s) = True Then
Return [String].Empty
End If
Dim builder As New StringBuilder()
Dim slug = input.Trim().ToLowerInvariant()
For Each c As Char in slug
Select Case c
Case ' '
builder.Append("-")
Case '&'
builder.Append("and")
Case Else
If (c >= '0' And c <= '9') OrElse (c >= 'a' And c <= 'z') And c != '-')
builder.Append(c)
End If
End Select
Next
Return builder.ToString()
End Function