MSDN said, depressed, don't know if there is any other way, is it really use of cookie
Info: ASP Session Object Can't Be Accessed by Isapi DLLS
Summary
ISAPI Filters and Extensions Do Not Have Access To ASP Intrinsic Objects. This Includes The ASP Session Object.
More information
The ASP intrinsic objects, including the session object, are instantiated when Asp.dll processes an ASP page. When ISAPI filters and extensions run, the intrinsic objects for a given session do not exist. For this reason, it is not possible for an ISAPI Dll To Access Information Stored In A Session Object.
If it is desirable to share information between ASP and ISAPI, and numerous techniques may be used to do so The best mechanism for sharing data may be through the use of cookies ASP can set and retrieve cookies as follows..:
<% Response.cookies ("VisitorID") = 49%>
<% = Request.Cookies ("Visitorid")%>
This Can Also Be Accomplished in An Isapi DLL AS Described in The Following Microsoft Knowledge Base Article:
168864 IMPLEMENTING COOKIES IN ISAPI
IT is also Possible to Share Information Between Asp and isapi by passing arguments along with the requested URL, Resulting In A Get Request:
http://server/vdir/some.asp? firstname = robert & lastname = duke
