Hi all,

I have had this book sitting on my shelf for a while, but have just gotten around to reading it over my holiday vacation. So far, so good...

I have been getting into LINQ for the past few weeks, and have had the idea that I might try to recreate the project in the book using .NET 3.5 and LINQ. I'd like to know -- from those of you who've gone through the book already -- how difficult do you think this might be to pull off? Should I even try, or should I just work through the project as written?

I await your thoughts...

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You could add LINQ in a few small places just to play with it. One of the problems of a 3 tier model is that it's hard to decide on how to keep the DAL isolated from the BLL while leveraging technologies that want to span those 2 layers.

A case could be made to merge some of the functionality of the DAL and BLL into one layer. This boils down to a religious question and I personally don't like purist viewpoints that require empty shell BLL classes just to keep the abstraction model clean.

If you don't know what I'm talking about, please ignore me. It's getting late :-)

By the way, there are many flavors of LINQ and not just "LINQ to SQL". You also have LINQ to XML, and LINQ to objects, etc.

I can't wait for the Entity Framework, which is coming soon. That's similar to Object Relational Mapping (ORM) systems. The idea is that you get to work with objects without worrying about the SQL.

Eric

Yes, you've made some good points here. It would probably be easy to do some light experimenting with LINQ on this project as it stands now.

Like you, I am anxiously awaiting the Entity Framework and LINQ to Entities. That should be huge -- really revolutionary. I could see at that point going back and retrofitting the entire project with L2E as a learning exercise, probably using most of the existing BLL. That's probably going to be Edition 3 of this book, don't you think?

Not sure if I agree with your other point about existing LINQ functionality interfering with the 3-tier architecture. LINQ is a pretty decent ORM just as it stands right now. With LINQ to SQL, it's pretty easy to build a clean DAL, and to put business rules into partial classes that reside separately from the DAL. But, as you point out, the entities that L2SQL creatses do closely mirror the DB schema, whereas L2E should make total abstraction from the underlying data store really easy.

This is my personal take on EF and I don't know know what Marco would say, but I can't see retrofitting EF into this particular site. I'd possibly re-use some of the code, but I'd probably give the new ASP.NET MVC pattern a try along with EF. The MVC model would require a much different architecture and it really wouldn't be very similar to what we have today.

MVC plays better with SOA, and less good with traditional 3-tier designs. It's funny that we're moving away from 3-tier already. The world is moving too fast, I think.

Anyone that is interested in Object Relational Mapping (ORM) might be happy to hear that Paul Wilson's cool ORMMapper is now open source. You can google for more on that.

Here's the writeup I did on ORM some time ago:
www.ericengler.com/downloads/orm.doc

I disagree that LINQ to SQL is ORM. LINQ is just a data access method. There's no mapping between objects and relational tables - at least this isn't built in. That's where EF comes into play. You're right that LINQ can fit into the DAL and you can do your own mapping - probably in the BLL.

You can keep the 3-tier model going with LINQ itself. But the EF might end up replacing the DAL and BLL with one black box - I talk about that in my ORM paper referenced above (it doesn't mention LINQ but the ORM ideas apply). Despite what the EF masters are saying, it still seems quite a lot like ORM to me.

I don't mean to downplay the significance of LINQ. But it's not especially exciting to me until the picture is augmented by supporting technologies. And the upside-down SQL takes some getting used to!

Eric