OO Design, Physical Implementation, DAOs

From: oj (oaguayo75_at_yahoo.com)
Date: 10/20/04 

Date: 20 Oct 2004 09:48:43 -0700

I'm just starting to wrap my mind around application programming from
the OO perspective. I've been asked to attempt to design and implement
a small web application based on OO prinicipal. All previous
development was completed by a third party group of programmers who
chose to not include a business object layer into the development
process.

I recently purchased a couple of books to help get me started:
Beginning C# Objects by Barker and C# adapted version of the GoF
Design Patterns book. I have to admit with little to no background in
OO design I attempted to read the Design Patterns book and realized it
was a tad over my head. I decided to get my feet wet with Barker's
book and have learned enough over the past few weeks to get a decent
handle on how to determine and model my domain class objects,
attributes, and behaviors.

Currently, the presentation layer(aspx pages), within our existing
application, talks directly to the DAL(made of DataAccess component
and DataSet classes) via the C# code behind pages for each. Over the
past year I've been maintaining this structure. Now on entirely new
project I'm being asked to design and implement an additional layer in
addition to the presentation and DAL layers, and I'm having trouble
understanding how to connect them. Oh yea, did I mention I'm working
on my own as my non-profit employer can only afford one programmer at
this time. Fun! Fun!
I have a many questions regarding the problem I've been given but here
are just a few:

1. On a high level is creating data access component classes made up
of DataAdapter objects, Command objects, and sql statements which are
mapped to datasets and talk directly to my SQL Server 2000 database
the proper way to constuct a DAL? If not where can I find
instruction/examples on the proper way to construct the DAL?

2. What is the role of data access objects in OO design? Are these
purely DAL components? Or if I have a domain class which potentially
has a collection of records as an attribute is it alright to create
this collection as a DataTable or an array of DataRows?

3. I'm probably completely off on #2, where can I find
instruction/examples on the physical implementaion of OO model? I'm
not understanding how I'm going to physically get data out of the DAL
into my objects and then get that data out of my objects and presented
to the GUI.

4. Currently, DataSet objects are instantiated in the aspx code behind
pages and datatables, within the dataSet, are bound to controls like
datagrids and datalists which works very nicely. How is this done when
working with objects and collections of objects?

Sorry about the longwinded post, but I need someone to check my
understanding before I go any further.

Any information is appreciated.

oj

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