CODEWITHSUNDEEP
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PostgresQLNewb
PostgresQLNewb

Reputation: 339

ASP.NET: Application lifecycle, static variables

A class in my ASP.NET website needs to access a database table multiple times for every request. The database table should rarely change, if ever. Maybe a couple times a month.

In the static constructor of the class, the table is fetched from the DB and cached in a static local variable. Whenever the class needs to access the table, then, it just uses the cached, static version.

My question concerns the lifespan of this cached, static version of the table.

I understand that it's fetched the first time the class is instantiated or a static method in the class is used. But how often does this occur on the web server? What if the table changes and we want to reset this static version of the table?

Basically, I'm wondering, is this table fetched once and then only refetched each time I restart IIS? What, with regard to the site and IIS, will trigger this static class to reset, causing the static table to be refetched?

Upvotes: 2

Views: 2719

Answers (3)

Grant Thomas
Grant Thomas

Reputation: 45058

I'd recommend using the ASP.NET cache itself, rather than having variables for each particular cache item (a single table right now, but I'm sure there's room for growth); this way you can specify expiration, among other things, such as dependencies.

You can get information on the cache here, and more specifically, using the cache here.

To answer your question about the life-cycle, or expectancy of a local variable, see this link, which should do a better job of explaining the innards than I.

Upvotes: 1

Martyn
Martyn

Reputation: 1476

Basically, I'm wondering, is this table fetched once and then only refetched each time I restart IIS?

Yes, you've got that spot on. Essentially, restarting IIS will cause your static variable to be "refreshed". If you use a static variable to store this kind of thing (which may not be the best solution, but I'm trying to directly answer your question without getting sidetracked), I would advise you build some code into your data layer so that your static variable is updated each time the database table in question is written to. This will mean that you dont need to bounce the server each time you update it.

Its also worth remembering that static variables are shared across all client requests, this can often lead to some unpredictable multi-threading errors.

Upvotes: 0

n8wrl
n8wrl

Reputation: 19765

Rather than a static variable on a class, why not make add this to the 'Application' collection? It's lifetime is well understood (the life of the website) and can easily be recycled by touching web.config. Populate it in your Application_Start method of global.asax.

Upvotes: 1

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