Deleting a Subset of Session Variables

When using Sessions to store variables in, I use a naming convention - for example, for all Customer related info I prefix the session variable with the substring Customer. (so for the CustomerID it would be Customer.ID, the customer username would be Customer.Name, etc.) This is very useful when viewing the session objects as you can see the related objects straight off.

The problem I had the other day was that I wanted to remove only those items from the Session which were prefixed SW.. So first off I used the following code:

'---------------------------------------

Session("SW.1")="Test 1"

Session("SW.2")="Test 2"

Session("Other")="Other"

For Each SessionItem in Session.Contents

If Left(SessionItem,3) = "SW." then

Session.Contents.Remove(SessionItem)

end if

Next

'---------------------------------------

This seems fine, but when it's run, what happens is that SW.1 is removed, but SW.2 is NOT removed. Why? I'm not exactly sure, but I guess that the index is then reset so that SW.2 is now where SW.1 was, and seeing as we have iterated past that item in the For Each...Next statement, the loop just moves to Other, missing out SW.2 altogether! Eek!

So to get round this I wrote the following function, which will properly delete all Session variables that begin with a specified substring:

'---------------------------------------

function SessionRemoveSelected(sItemPrefix)

'/////////////////////////////////////////////////

' Remove Selected Items starting with sItemPrefix

' from the Session. e.g. SS. will remove SS.ID and

' SS.NAME but not CustomerID Returns True or False

' depending on whether any items where removed.

'---------------------------------------

' sItemPrefix [string] : Item Prefix

'/////////////////////////////////////////////////

dim arySession()

dim lCount, lPrefixLength

dim SessionItem

dim blnResult

lCount = -1

lPrefixLength = len(sItemPrefix)

blnResult = false

' temporarily store in array items to remove

For Each SessionItem in Session.Contents

if left(SessionItem,lPrefixLength) = sItemPrefix then

lCount = lCount + 1

redim preserve arySession(lCount)

arySession(lCount) = SessionItem

end if

Next

' remove items

if IsArray(arySession)and lCount >= 0 then

for lCount = LBound(arySession) to UBound(arySession)

Session.Contents.Remove(arySession(lCount))

next

blnResult=true

end if

SessionRemoveSelected = blnResult

end function

'-------------------------------------------------