Add or replace a query string parameter in classic ASP

Question

I have a set of links in header.asp which is included on every page; these links have their href attribute set to whatever the current page is plus a linkID param. Sometimes the page the link references will have query string params, but other times it won't. If the current page URL contains the linkID param already I need to replace it, otherwise I need to add it to the current URL.

I am concatenating Request.ServerVariables("SCRIPT_NAME") and Request.ServerVariables("QUERY_STRING") into a variable pagename to get the current page URL. Unfortunately, I'm using classic ASP/VBScript.

I think I need to use reg ex but am not expert in it, especially not in classic ASP. The problem comes when I need to replace the element as the linkID param's value can vary so the simple Replace method won't work.

A concrete example of a string you currently have in the header.asp, a URL of the current page and the disired result would help. You get much faster answers by doing the leg work of creating the test data, rather then making us imagine that up for you. — AnthonyWJones, Aug 03 '09 at 10:44
Thanks for the advice; I'll make sure any future questions are more helpful for the reader. — Rich, Aug 03 '09 at 11:03

Dave Anderson · Accepted Answer · 2009-08-03T10:54:58.110

You can check if the parameter is already in the querystring Request.QueryString("linkID") = "" and simply append if it isn't and use a function to update the value if it is there. Something like this will be fine as long as you don't have a massive number of parameters and you're not having to optimise massively but then you would probably not be using ASP.

Function updateQueryStringParam(key, value)

  Dim qs, x

  For Each x In Request.QueryString
    qs = qs & x & "="

    If x = key Then
      qs = qs & value & "&"
    Else
      qs = qs & Request.QueryString(x) & "&"
    End If
  Next

  If Len(qs) > 0 Then
    If Right(qs, 1) = "&" Then
      qs = Left(qs, Len(qs)-1)
    End If
  End If

  updateQueryStringParam = qs

End Function

You could create another function call for the check and then update using the function above;

Function setQueryStringValue(key, value)

  Dim qs

  If Request.QueryString(key) = "" Then
    If Len(qs) > 0 Then
      qs = qs & "&"
    End If
    qs = key & "=" & value
  Else
    qs = updateQueryStringParam(key, value)
  End If

  setQueryStringValue = qs

End Function

in your function ```setQueryStringValue``` variable ```qs``` does not have a value initially, so ```Len``` will always be 0. — Michiel van der Blonk, Oct 27 '17 at 16:55

Add or replace a query string parameter in classic ASP

1 Answers1

Linked