How do I replace the value in this query string

Hello everyone, I have this url:
www.example.com?sid=1&id=2&test3=3
I am writing logic to replace the query string id. But because sid also contains the character id, my url became:
www.example.com?sid=4&test3=3
Any suggestion how I could fix this? Here is the code I used to replace:
If newUrl.IndexOf("id") > -1 Then Dim oldValue As String oldValue = HttpContext.Current.Request.QueryString(row("id")) newUrl = newUrl.Replace("id" & "=" & oldValue, "id" & "=" & "4") End If Thanks.