关于释放session的两篇文章（二）

核心提示：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 PRefi

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