static vars/ com/ win-service: What is the best solution?

[David Boaz]

Hello all,
I have an middleware that has to be accessed from two different
applications, win-form and asp-form. the middleware uses a file to store and
retrieve information. I want to economize the IO and to read/write to the
file only when the application stops, and meanwhile to store the information
in memory data structure.
My program has evaluated throw the following steps:
1) I made the middleware as a dll project. The data structure was static,
and was initialized on the initialization of class (on the static
constructor). the problem was that the two application has created two
different data structures, and were not synchronized.
2) I converted the middleware into a COM object, and I enforced the maximum
pool size to be 1. In this case everything was ok, but I looked for a better
solution, without enforcing the max pool size (too sophisticated, not
straight forward).
3) I converted it to a windows service (an exe file). The problem now is
that I can not create references from the applications to the middleware
(only dll are allowed as references).

My question is what is the best solution for the above problem?
Any one another type of solution?

thanks, David