QueryString Manipulation Using VB.NET

[sirjohnofthewest]

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)

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

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.

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:

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

Yes! It's that easy!