Good layered architecture with validation and LINQ (+ WCF?)

Evert wrote:

Does anybody have a good example/guide for using LINQ in a layered
architecture with maybe WCF?

It's in general not good practise to use a service as a tier. Services
are standalone applications, so should be seen as vertical slices of
your application, not horizontal slices of your application.

FB

--
------------------------------------------------------------------------
Lead developer of LLBLGen Pro, the productive O/R mapper for .NET
LLBLGen Pro website: http://www.llblgen.com
My .NET blog: http://weblogs.asp.net/fbouma
Microsoft MVP (C#)
------------------------------------------------------------------------

Feb 4 '08 #2

=?Utf-8?B?RXZlcnQ=?=

Can you explain me why a service is not a Tier? What do you mean with
horizontal and vertical? is there a good site which explains this?

Thanks in advance,

Evert

"Frans Bouma [C# MVP]" wrote:

Evert wrote:

Does anybody have a good example/guide for using LINQ in a layered
architecture with maybe WCF?

It's in general not good practise to use a service as a tier. Services
are standalone applications, so should be seen as vertical slices of
your application, not horizontal slices of your application.

FB

--
------------------------------------------------------------------------
Lead developer of LLBLGen Pro, the productive O/R mapper for .NET
LLBLGen Pro website: http://www.llblgen.com
My .NET blog: http://weblogs.asp.net/fbouma
Microsoft MVP (C#)
------------------------------------------------------------------------

Feb 4 '08 #3

It's in general not good practise to use a service as a tier.
Surely WCF is precicely that though; an abstract bridge between
(generally physical/horizontal) tiers For instance, a smart-client
using WCF to access data from a WCF service over (typically) http[s].
Perfectly normal and indeed the textbook use-case.

For specific scenarios, this does exist - but in quite controlled
scenarios - google for "LINQ to Amazon" for example; not WCF, but a
similar fundamental principle - but it takes a lot of plumbing code.
http://weblogs.asp.net/fmarguerie/ar...to-Amazon.aspx

In the more general sense, I know what the OP is asking for (something
akin to a data-context for a WCF interface), and unfortunately I
haven't seen anything that really fills that gap - but the biggest
barrier is that LINQ really works within a logical (vertical) tier
where you can just about get away with allowing ad-hoc (i.e. not
formally defined up-front) queries, since you are in the same column.
It doesn't work well accross physical (horizontal) tiers, where you
normally want to have well-defined interfaces. That said, the REST
offering in 3.5 may offer some interesting possibilities, since that
is a bit less formalised (allow for better composability); but a
double edged sword...

Marc

Feb 5 '08 #4

Evert wrote:

Can you explain me why a service is not a Tier? What do you mean with
horizontal and vertical? is there a good site which explains this?

Vertical means that you have a full application with layers which has
an interface you can utilize as a service. Horizontal means that you
have a layer in your application which happens to be consumable as a
service.

The downside of horizontal usage of a service is that you have a lot
of data-traffic between tiers in formats which are used internally in
your application. In short: it's very inefficient.

Services should be seen as standalone applications you're utilizing in
your application. See these presentations by Gregor Hohpe:
http://www.infoq.com/presentations/h...oa-development
and
http://www.infoq.com/presentations/h...-conversations

I'm sure after the first one, you'll understand what I mean :)

FB

>
Thanks in advance,

Evert

"Frans Bouma [C# MVP]" wrote:

Evert wrote:

Does anybody have a good example/guide for using LINQ in a
layered architecture with maybe WCF?
It's in general not good practise to use a service as a tier.
Services are standalone applications, so should be seen as vertical
slices of your application, not horizontal slices of your
application.

--
------------------------------------------------------------------------
Lead developer of LLBLGen Pro, the productive O/R mapper for .NET
LLBLGen Pro website: http://www.llblgen.com
My .NET blog: http://weblogs.asp.net/fbouma
Microsoft MVP (C#)
------------------------------------------------------------------------

Feb 5 '08 #5

Marc Gravell wrote:

It's in general not good practise to use a service as a tier.
Surely WCF is precicely that though; an abstract bridge between
(generally physical/horizontal) tiers For instance, a smart-client
using WCF to access data from a WCF service over (typically) http[s].
Perfectly normal and indeed the textbook use-case.

'tier' in general means horizontal layer, not vertical pillar.

See my links in the other post :)

FB
--
------------------------------------------------------------------------
Lead developer of LLBLGen Pro, the productive O/R mapper for .NET
LLBLGen Pro website: http://www.llblgen.com
My .NET blog: http://weblogs.asp.net/fbouma
Microsoft MVP (C#)
------------------------------------------------------------------------

Feb 5 '08 #6

Services should be seen as standalone applications you're utilizing

in
your application. See these presentations by Gregor Hohpe:
[links to some SOA presentations]

Now, if only we (at large) could agree on a single interpretation of
SOA ;-p

Feb 5 '08 #7

hence horizontal not vertical.
or do I mean vertical not horizontal?
"things that are arranged vertically, and have the same horizontal
reference"

I'm managing to confuse all 3 of us now... more coffee...

But if you can see past my random word swaps, I think I have a
sensible point in there somewhere... probably well hidden...

Feb 5 '08 #8

Marc Gravell wrote:

Services should be seen as standalone applications you're utilizing
in your application. See these presentations by Gregor Hohpe:
[links to some SOA presentations]

Now, if only we (at large) could agree on a single interpretation of
SOA ;-p

Hehe, that would indeed be a first ;). Just imagine if such an
agreement would arise... how many book publishers would go out of
business, eh? ;)

FB

--
------------------------------------------------------------------------
Lead developer of LLBLGen Pro, the productive O/R mapper for .NET
LLBLGen Pro website: http://www.llblgen.com
My .NET blog: http://weblogs.asp.net/fbouma
Microsoft MVP (C#)
------------------------------------------------------------------------

Feb 6 '08 #9

Message board layered architecture 2-tier or 3-tier?

Just to add a thought; perhaps Astoria is the answer here? Currently
CTP, but it seems to offer much of what you are talking about...? I
haven't had time to play with it yet, though...

Marc

Feb 6 '08 #10

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