DonXML has an interesting article over here that got me thinking about a technique I have been using for years now, and I’m not sure I’ve seen much written about it.
The basic tenet begins like this: I avoid session like the plague (not sure why except I have visions of some abuses I have seen... like full DataTable’s stored in session). The only time and I mean the ONLY TIME I use Session is if I have a value that needs to be associated with a user across the WHOLE site. As a result I really try to design my model where there are minimal values that need to be associated with a user site-wide.
What I have seen is that values come in 3 basic variations as far as Web site variables go: Values associated with a user everywhere, values associated with a user necessary for a few pages, values that really are application level values.
My suspicion about "Values associated with a user everywhere" is that they are not as prevalent and are often the result of programmers either not fully understanding web apps, they just aren’t thinking things through, or they are pushing a value into session site-wide when they only need it in a couple places. Treat Session like you do ViewState: it is a snake (maybe a poisonous one) that while necessary to kill the rats in your back yard due to the citrus trees, you don’t want a dozen snakes in the backyard either... Only use the number of snakes that you need (if you have no rats then 0 is the perfect number of snakes). So the lesson here is to really look at your user-related values: determine if they really are used everywhere, and determine if they need to be available in memory the whole the user is on the site.
For values associated with a user necessary for the a few pages, I tend to use cache, or I do use Session (but I clean up immediately after I’m done). When I use Cache I factor in the user’s Session ID. The thing I like about Cache is that I have a much richer set of expiration options. Session sticks while a user is clicking around the site... Cache let’s me absolutely set an expiration time. I also am aware of the fact that Cache can be unloaded early (so I use Cache as a temporary place for a value knowing that I may need to retrieve it again). If it’s something that isn’t stored elsewhere then into Session it goes (even if I have to delete that Session var later). It’s really about managing the data in memory.
For the application type values, I usually forget about the whole Application mechanisms (you might use them, but I do something else), I like to use static/shared values on individual classes. This has the effect of better organizing your code (and if you do any else with the class it simplifies things... I suspect some automated test guys would agree with me on this point). Why mention these here? Well I have seen my share of things that were really application related or indexed application related (such as storing this customer’s company info in session... that really should be either a cache or a static, and it should be retrievable by some company id).
Don’s post was originally spawned by the new Velocity cache from MS. Honestly the only comment I have on it is that I wish they had chosen a different name. I hear Velocity and I think about the text template engine (the one for Java... but the one for .NET is nvelocity)
Print | posted on Tuesday, June 10, 2008 11:15 AM