RE: ASP.Net, caches, scope of statics

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Hi Mark,

Regarding on the ASP.NET Cache question you mentioned, here are some of my
understanding:

** ASP.NET Cache is per AppDomain based. Since each ASP.NET application is
scoped at AppDomain level(just like normal .net application), different
ASP.NET application instances(such as webfarm instances) can not share
Cache data.

** Sure, you can use some custom Class and Static member properties to
cache data instead of built-in Cache, the scope is the same(within the same
appdomain). However, the advantage of ASP.NET Cache is that it provide
multiple Cache Dependencies that can help you add auto-expire/invalidate
support. For example, you can use time based or data based cache dependency
so as to make a cache item be invalidated after a certain timespan (or a
certain database table is changed).

** If you have requirement to share data among webfarm server instances. I
think using database is still the preferred approach.

Sincerely,

Steven Cheng

Microsoft MSDN Online Support Lead


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--------------------
From: =?Utf-8?B?TWFyaw==?= <mmodrall@xxxxxxxxxxxxx>
Subject: ASP.Net, caches, scope of statics
Date: Wed, 16 Apr 2008 14:58:01 -0700

Hi...

At least by the group title, this seems like a question for
dotnet.framework.aspnet.caching but that group seems pretty slow.

I'm trying to sort things out with a co-worker. We've got some classes
that
implement some in-memory caches with static Hashtable members. My
understanding is that a static Hashtable may be shared between threads in
the worker process but that it won't span multiple worker processes.

I'm not sure about the System.Web.Caching.Cache class. You can't
instantiate one of your own, so I'm not sure if there's something buried
down
in the framework to make this work across processes in a garden.

Also not sure if you can achieve better sharing by putting a C# class in
the
Application scope (sorry if that's nonsensical; I haven't actually put
objects in application scope since classic asp).

Thanks
Mark



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