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4GuysFromRolla.com : ASP FAQS : Session Object


Question:

Can I store VBScript class objects in a Session variable?


[Print this FAQ]

Answer: This question was posed by Petr Stahel on the ASPMessageboard (Read the post!). Petr asked:

------------------------------------

"I am trying to store a VBScript class in a session variable, but it doesn't work. Essentially, I want to be able to do:

if not IsObject(Session("objST")) then
Response.Write "not From session"
set objST = new clsSortableTable
set Session("objST") = objST
else
Response.Write "From session"
set objST = Session("objST")
end if

Is this at all possible?"

------------------------------------

Regular ASPMessageboard.com poster and ASPFAQs.com contributor Bill Wilkinson answered Petr's question as follows (Read the post!)

------------------------------------

"I'm afraid it can't be done. This is because VBS classes are NOT true classes. They are really just in-memory collections of info, and there is no way to guarantee (for example) that an instance that is stored in one page will even come close to matching the class definition in another page.

"Sorry, but the best you could do would be to convert your VBS class instance into an array or a delimited string or some such in order to save it. And then you restore it from that form into an instance in the receiver.

"To illustrate the problem, consider this ASP page:

**** pageOne.asp ****
<%
Class Demo
public name
End Class

Set d = New Demo
d.name = "Petr Stahel"
Set Session("Petr") = d
%>

"And then here is the next page that gets used:

**** pageTwo.asp ****
<%
Class Demo
public emailAddress
public userName
End Class

Set d = Session("Petr")
%>

"Enough said? Unlike TRUE COM classes, there is no way to ensure that a VBS class will remain unchanged from one usage to the next. Another way of saying this is that VBS class instances are not "first class" objects."

------------------------------------

Thanks for the great response, Bill!


FAQ posted by Scott Mitchell at 9/3/2002 10:23:06 PM to the Session Object category. This FAQ has been viewed 61,976 times.

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