Removing Session variables

Colonel Angus · August 26th, 2004, 10:52 AM

I have a page where I pass in Date values in Session variables. I use them to generate a report on the page. If I just copy the value into the viewstate and remove from the session, it works fine unless I refresh the page.

I am currently not using the viewstate, and keep the value in the session. This works fine (refreshes are ok), but I want to remove these values from the Session when I'm done with them - when the user leaves the page. How is this done? I don't want unnecessary Session values using up memory until they log/time out.

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In God we trust, everything else we test.

bmains · August 26th, 2004, 11:02 AM

I believe the session has a remove method, but if not, do:

Session("Value") = Nothing

Or Session.Abandon()

Brian

Colonel Angus · August 26th, 2004, 11:25 AM

I was using that approach, but when I refreshed the page, I lost my values (and subsequently broke my code)

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In God we trust, everything else we test.

bmains · August 30th, 2004, 07:34 AM

Hey,

Isn't that the idea for removing session values, to lose the values? Could you post any code and let me know what your approach is?

Brian

Colonel Angus · August 30th, 2004, 09:03 AM

Brian-

My code goes like this (in the Page_Load procedure)

Code:

If Not Page.IsPostBack Then
   viewstate("Date1") = Session("Date1")
   viewstate("Date2") = Session("Date2")
   'Clean up session
   Session.Remove("Date1")
   Session.Remove("Date2")

   obj.StartDate = CDate(viewstate("Date1"))
   obj.EndDate = CDate(viewstate("Date2"))

   results = obj.GetReportData
End If

Postbacks are ok, but when I refresh the page, the date values are lost. I get the "SqlDateTime overflow. Must be between 1/1/1753 12:00:00 AM and 12/31/9999 11:59:59 PM." error.

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In God we trust, everything else we test.

stu9820 · August 30th, 2004, 09:14 AM

Clean up your sessions in the global.asax:

protected void Session_End(Object sender, EventArgs e)
{

}

Colonel Angus · August 30th, 2004, 09:19 AM

Stu-

Is it a question of where I remove the Session variables or when?

If I implement a procedure in the Session_End procedure of global.aspx, I have to wait until their Session times out or until they log out (I explicitly abandon the Session in the log out procedures). I want to only keep these values in the Session so that I could pass them from the previous page.

I don't like to keep values in Session once they aren't needed anymore in order to free up the resources.

-Colonel

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In God we trust, everything else we test.

Colonel Angus · August 30th, 2004, 09:47 AM

FYI, I also tried this:

Code:

Private Sub CleanSession(ByVal sender As System.Object, ByVal e As EventArgs) Handles MyBase.Unload
        'Clean up session
        Session.Remove("Date1")
        Session.Remove("Date2")
End Sub

With the same error.

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In God we trust, everything else we test.

bmains · August 30th, 2004, 02:36 PM

Hey,

Are you storing these values so that they survive page redirects and such (spanning across multiple pages)? If so, if the session doesn't work, you can use the cache... may be more efficient, and easier to use. It has an application-level scope; however, there are tricks to make it unique to a user.

Brian

Colonel Angus · August 31st, 2004, 07:12 AM

I'm using the session to avoid bloating my querystring.

The scenario is a report: On the first page the user selects the criteria for the report, the second page displays the report data. I use the session values to pass 2 dates and a list of integers from the first page to the second.

I have a band-aid solution that involves a try-catch block. If the date values are lost, the user is redirected to the criteria (first) page.

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In God we trust, everything else we test.