[Mono-list] Re: Consuming unmanged code, global/static variables, ASP.NET pages

[Robert Jordan]

Chris,

> Looking for some guidelines on consuming some of our library (in C) into
> .NET for use with ASP.NET pages
> 
> I'm concerned about our global and static variables that are needed in some
> of our libraries.  In a single threaded C# application this would be no
> problem.  Initialize the libraries at startup, destroy on close.
> 
> But for ASP.NET pages, how would I handle initialization, since multiple
> pages are being served at the same time making use of these libraries?

Are your native libraries thread safe? If yes, you usually don't
have to care about the initialization. If they are not: welcome to a
world of pain.

> Would I initiailze for each page request as needed in the C# code behind
> page?  Or is this going to have problems when multiple requests are issued?

It won't work. Go ahead and fix the native library. Everything
else is a waste of time.

 > Also what about a function that contains a static variable?

You have to rewrite them to use a TLS slot instead of the
static variable. If the content of the static variable is
thread invariant, a lock for its initialization might be sufficient.

The same has to be done with static variables outside
of functions as well.

> Basically these are the questions I have, but I just can't find any
> resources to explain how ASP.NET applications are threaded, and how it would
> effect consumption of unmanaged libraries.  If anyone can even point me in
> the right direction I'd be very grateful.

The threading model of ASP.NET is quite straightforward for
the developer: one cannot predict by which thread the request
will be handled. This implies that the ASP.NET consumer has
to deal with concurrency all the time.

Robert