How To manipulate QueryString Using VB.NET

This function will give you 100% control over the QueryString -- perfect for programmers who use QueryString manipulation a lot.

I wrote this function when I kept having to change values of the QueryString and remove some, add some, etc., etc..

It takes four (4) parameters:

oldUrl = the current QueryString you would like manipulated
qsName = the name of the QueryField you would like to modify/remove/add
newValue = the new value you would like for the QueryField. set to "" if removing
del = an optional integer bit flag; if set to 1 it will remove the QueryField/QueryFieldValue from the QueryString.

Here is the code, enjoy! (I am always welcome to new suggestions)


Code: ( vbnet )
Function ChangeValue(ByVal oldUrl As String, ByVal qsName As String, ByVal newValue As String, Optional ByVal del As Integer = 0) As String

Dim newUrl As String = ""

' Check if the [qsName] is currently in the [oldUrl]
If InStr(oldUrl, qsName & "=")

oldUrl += "&"

Dim pos1 As Integer, pos2 As Integer

If del = 1
pos1 = oldUrl.IndexOf(qsName & "=")
pos2 = oldUrl.IndexOf("&", pos1) + 1
Else
pos1 = oldUrl.IndexOf(qsName & "=") + qsName.Length + 1
pos2 = oldUrl.IndexOf("&", pos1)
End If

Dim chunk_1 As String = oldUrl.SubString(0, pos1)
Dim chunk_2 As String = oldUrl.SubString(pos2)

If del = 1
newUrl = chunk_1 & chunk_2
Else
newUrl = chunk_1 & newValue & chunk_2
End If

newUrl = newUrl.SubString(0, (newUrl.Length - 1))

Else

If del = 1
Return oldUrl
End If

' Append the new value to the [oldUrl] and make it a [newUrl]
If oldUrl.EndsWith("?")
newUrl = oldUrl & qsName & "=" & newValue
ElseIf InStr(oldUrl, "?") AndAlso oldUrl.EndsWith("?") = False
If oldUrl.EndsWith("&")
newUrl = oldUrl & qsName & "=" & newValue
Else
newUrl = oldUrl & "&" & qsName & "=" & newValue
End If
Else
newUrl = oldUrl & "?" & qsName & "=" & newValue
End If

End If

Return newUrl

End Function


Here is an example:
We have the querystring

Code: ( text )
http://www.yourdomain.com/search.aspx?fulltext=cat&author=bill+nye&type=scientist&age=45


Now I want to change the "fulltext" to "dog" and the "author" to "bob dole"
Also, I want to remove "type" from the QueryString.

Code: ( vbnet )
Dim newUrl = Request.RawUrl.ToString()
newUrl = ChangeValue(newUrl, "fulltext", "dog")
newUrl = ChangeValue(newUrl, "author", "bob dole")
newUrl = ChangeValue(newUrl, "type", "", 1)


The QueryString would now look like this:

Code: ( text )
http://www.yourdomain.com/search.aspx?fulltext=dog&author=bob+dole&age=45


Yes! It's that easy!