Gerade habe ich einen interessanten Artikel gefunden der zeigt, wie man einen Parameter aus der Querystringauflistung entfernen kann.

Public Sub RemoveQueryString(ByVal Req As HttpRequest, ByVal strKeyToDel As String, ByVal http_Context As HttpContext)
Dim nvc As System.Collections.Specialized.NameValueCollection = New System.Collections.Specialized.NameValueCollection(Req.QueryString)
Dim sPage As String = Req.ServerVariables("SERVER_NAME") & Req.ServerVariables("SCRIPT_NAME")
nvc.Remove(strKeyToDel)


Dim strNewURL As String = Req.Path
Dim sSeparator As String = "?"
Dim sKey As String
For Each sKey In nvc
If sKey <> Nothing Then
Dim sValues As String() = nvc.GetValues(sKey)
Dim sValue As String
For Each sValue In sValues
If sValue <> Nothing Then
strNewURL &= sSeparator
strNewURL &= sKey & "=" & sValue
sSeparator = "&"
End If
Next
End If
Next
If nvc.Keys.Count < 1 Then
strNewURL &= "?"
End If
http_Context.Current.RewritePath(strNewURL)
End Sub

Gefunden habe ich den Code unter http://www.codeproject.com