I'm storing a token in a session variable. I launch a report that needs this token in a new ASPX page by using the javascript windows.open function. When this new page loads the HttpContext.Current.Session is null.
I have gotten around this by passing the token in the query string but activity in this window needs to keep the session of the parent window active and I'm not sure what the session object being null means for this scenario.
Any idea why the HttpContext.Current.Session object would be null by using window.open from javascript?
EDIT: I will add that this is a basic System.Web.UI.Page stored in a SharePoint library and the window.open function is called from a webpart. I'm thinking that this page may need to inherit from a base class to share the right context.
UPDATE: I've narrowed down that this is related to SharePoint. I moved the code that accesses the Session object into a web part. The web part works fine if put in a standard web part page but I have it added to a minimal page that only contains a ScriptManager, SPWebPartManager and a WebPartZone. The code runs but the session object is again null. My minimal page is missing something that makes the Session object available.
SOLVED: My minimal ASPX page needed to implement the IRequiresSessionState interface. After that the Session object is there.
I'm going to give the cred to Andrey since he offered the most useful information.
Technically, it's a different connection to the web site, that's why it's a different session. It's probably better to use Application cache instead of session if you want different windows to utilize the same session storage.
UPDATE: What you can do if you want to stick to using session state, is to write the session ID to a persistent cookie, this way the child window's call to the server will carry it along and you can retrieve SessionID from that cookie. IMPORTANT: Make sure you encrypt session ID ebfore putting into teh cookie to avoid session hijacking.