Architecture question
service app written to run on WM5 CF2 and would like some advice on
architecture. For this type of app, the runtime performance is crucial
in relation to startup time.
I have a Data Access Layer (DAL)
with various classes that provide the abstraction between business
objects and the persistence layer e.g. SqlCe. One class per business
object.
On top of that is the Business Logic Layer (BLL) that uses the DAL layer. This is impemented by normal classes.
And on top of that the Presentation layer implemented as a number of Forms that use the BLL layer methods only.
I
have also created a 'MyApplication' class with the singleton pattern.
When the class instantiates, it creates all the BLL classes, the
database connection as well as all the DAL classes i.e. it creates the
entire application infrastructure except forms on app startup.
Each
of the DAL classes create, on instantiation, a host of SqlCeCommand
objects, hooked up to the single application-wide database connection.
For each unique query and SQL statement that I execute in my app, I
creat a command object with the parameterised SQL text. Each command is
also prepared at startup. The reason for this is that the app is
completely data-driven and I have found that the only way to enhance
runtime performance is to create and prepare the command objects at
startup. Startup obviously takes longer, but the data-driven
performance is way better this way. The downside is that the app is
more memory intensive because everything is held in memory. The end
result is that I have a large number of SqlCeCommand objects in memory,
all hooked up to the currently (always open) database connection.
However,
my forms are only created the first time it is needed, after that it is
simply 'Shown' again. They also follow a singleton pattern and is kept
in memory for later use.
Each of the layers sit in a different assembly.
All
code examples I have seen, show that the connection/command object(s)
are created when needed, used, and then disposed of again. I have tried
this but it killed the app's performance.
I would like some comments on this architecture and will appreciate if anybody could point to pitfalls, etc.
