As presented to the Milwaukee Alt.Net group on November 21st, 2011. UPDATE April 19, 2012: added some domain logic organization slides using Fowler's 4 basic patterns.

1. Implementing the
Onion Architecture
Gary Pedretti – Gary.Pedretti@Centare.com
4/19/2012
Logo, Design, and Company Information:© 2011 Centare Group, Ltd.
Slide Show and Notes Content: Creative Commons License, Gary Pedretti
Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.

2. About Centare
Consulting Services Organization
Primary focus on Agile, Mobile and Cloud
Individual and team based development
.NET, Java, and iOS technology stacks
Microsoft Gold Partner in ALM
Training, coaching, mentoring & team
building
Full Scrum.org course offering
Best practices training
Technical and business leadership strategies

3. Gary Pedretti
Solutions Manager, Agile Practice
Over 12 years in the software industry – DBA, Developer,
BA, Application Architect
Scrum: Team member, Scrum Master, Coach, Certified
Scrum Trainer for Scrum.org
http://blog.GaryPedretti.com/
@GaryPedretti
http://www.linkedin.com/in/garypedretti
MCPD 4.0 Web, MCTS 4.0 WCF/Web/Data Access, MCDBA MSSQL 2000, PSM, PSD .NET, PSD Java, CSM, MCPD 3.5 ASP.NET,
MCTS 3.5 WCF/ASP.NET/ADO.NET, MCTS SharePoint 2003 Infrastructure, MCPD 2.0 Enterprise, MCTS 2.0 Distributed/Web/Windows,
MCSD 1.1, MCAD 1.1, MOUS

4. Onion Architecture
S#arp
Implementing the Onion Architecture with
S#arp
Custom Code

5. Let’s Talk Business Logic….Domain
Logic…Behavior…

6. Fowler and “The Bible”
Four Domain Logic
Patterns

7. 1. Transaction Script – “Anemic Domain”
Organizes business logic by procedures where
each procedure handles a single request from
the presentation.
Little different from the Procedural paradigm
Is this Object-Oriented?

8. 2. Table Module – Object Model ~= Data Model
A single instance that handles the business logic
for all rows in a database table or view.
Think DataSet – if you built behavior around it
Differs from Active Record because it holds all
rows, not a single row

9. 3. Service Layer
Defines an application's boundary with a layer of services that
establishes a set of available operations and coordinates the
application's response in each operation
“Service” - arrrrrggggggghhhhhhhhhh

10. 4. Domain Model
An object model of the domain that incorporates
both behavior and data.
This is just Object Orientation!!!! That’s it!!!
This is also Domain Driven Design…kinda

11. Other Patterns
Where do these fit in?
Presentation patterns
Data Source patterns

12. Model View Controller…or MVx
Splits user interface interaction into three distinct
roles.
Is this presentation only?

13. Active Record
An object that wraps a row in a database table
or view, encapsulates the database access, and
adds domain logic on that data.
Isn’t this at the same level as a Table Module?
Still Object Model ~= Data Model

14. Let’s Talk Layers…and Tiers

15. Traditional Layered Architecture
Images:
http://jeffreypalermo.com

16. Traditional Layered Architecture – Anemic
Domain?

18. Image: http://jeffreypalermo.com

19. Key Tenets of Onion Architecture
The application is built around an independent
object model
Inner layers define interfaces. Outer layers
implement interfaces
Direction of coupling is toward the center
All application core code can be compiled and
run separate from infrastructure
Source: http://jeffreypalermo.com/blog/the-onion-architecture-part-3/

20. AKA “Ports and Adapters” or “Object
Structural” or “Hexagonal Architecture”
Image: http://alistair.cockburn.us/Hexagonal+architecture

21. AKA “Ports and Adapters” or “Object
Structural” or “Hexagonal Architecture”
Create your application to work without either a
UI or a database so you can
Run automated regression-tests against the
application
Work when the database becomes unavailable
Link applications together without any user
involvement
- Alistair Cockburn, http://alistair.cockburn.us/Hexagonal+architecture

22. If we were to represent the Onion
Architecture flattened…
Image: http://jeffreypalermo.com

23. If we were to represent the traditional
layered architecture concentrically…
Image:
http://jeffreypalermo.com

25. A Metaphor
Domain-Driven Design (DDD) – The Domain is
central to the system – Domain Model
Inversion of Control or Separated Interface -
Loose coupling based on interfaces at design
time, concretes only at runtime
Dependency Injection
Service Locator
Mocking – Application core can be compiled,
run, and tested with no infrastructure

26. What else is DDD about?
Establishing a Ubiquitous Language between
developers and the business
Context
Primitives of:
Entity
Value Object
Aggregate Root
Service
Repository
Factory
Again, good Object Oriented Design

27. Onion Architecture
S#arp
Implementing the Onion Architecture with
S#arp

28. S#arp: NOT the Korean Pop Band

30. S#arp History
Open source project
New BSD license
Billy McCafferty has been the primary contributor
Hosting
CodePlex
Google Code
github
Current stable release: 1.9.6
Latest release: 2.0

31. Components/Dependencies of S#arp 1.9.6
NHibernate 3.0
Fluent NHibernate 1.2
Castle Windsor 2.5.1
Microsoft Practices Service Locator 1.0
ASP.NET MVC 3

32. S#arp 2.0
NHibernate 3.2
Fluent NHibernate 1.3
Castle Core/Windsor 2.5.2/2.5.3
*.Web.Controllers will not be a separate project
ApplicationServices project renamed Tasks

33. So, what does S#arp give me?
“…this is a solid architectural foundation for
rapidly building maintainable web applications
leveraging the ASP.NET MVC framework with
NHibernate.”
Pre-configuration leveraging convention-over-
configuration and Fluent NHibernate Auto
Persistence Model
Extensible via Fluent NHibernate Convention objects

34. So, what does S#arp give me?
Tokenized T4 templates for scaffolding CRUD
forms-over-data applications
Additional layering goodness with the
CrudScaffoldingForEnterpriseApp templates
Controllers use Application Services/Tasks layer
which wraps Repositories, as opposed to dropping
Repositories directly into Controllers
Uses NHibernate Named Queries for additional
control and improved performance
Object validation framework

35. So, what does S#arp give me?
The Anti-LightSwitch for simple CRUD forms-
over-data applications – think:
What if VS LightSwitch didn’t suck??
What if it actually used best practices??
What if it really was as extensible as they claim??

36. Caveats and Compromises
DDD No-Nos:
Domain classes should inherit from
SharpArch.Core.DomainModel’s Entity (sets up
an integer key) or EntityWithTypedId<T>
Deep inheritance chain – Entity :
EntityWithTypedId<T> : ValidatableObject :
BaseObject – not very hip 
NHibernate.Validator reference in Core (Domain)
project by default
Domain classes have all virtual properties
because of NHibernate

37. Caveats and Compromises
Typical Open-source caveats
Some pieces are buggy
Luckily, primarily around the generated pieces – not the
framework itself
Some pieces are clunky
Code generation pieces have manual setup, clunky to
change
Database tables require manual setup – not a big deal,
but an obvious exclusion from all the automatic built-in
stuff
Documentation is relatively poor – especially because
of all the hosting transitions
Not an incredibly active project

38. S#arp Architecture Contrib Project
Additional support for common scenarios
Easy logging of any and all methods – via Assembly
Attribute
Transactions and Units of Work – via Method Attributes
Extends S#arp to work well outside the ASP.NET
environment
Uses AOP to do much of its work, via PostSharp
and Castle Interceptors
Current release: 0.2.0
Very inactive project – last check-ins in February
2011

39. S#arp Architecture Contrib Project
Planned features:
Support and Guidance for Windows GUI and
Windows Service Applications
Logging Controlled by an Attribute
NHibernate Transaction and Session Management
Attributes for Windows Applications and Services
Transactions Optionally Participate in
System.Transaction Transactions
(TransactionScope)
Support and Guidance for Using Rhino Security (not
available in first beta)

40. Onion Architecture
S#arp
Implementing the Onion Architecture with S#arp

41. Your First S#arp Solution
Install MVC 3 - http://www.asp.net/mvc/mvc3
Install Templify -
https://github.com/endjin/Templify/downloads
Download and install Templify template for
S#arp 1.9.6
Rt. Click a folder in Windows Explorer and
“Templify Here” – choose the S#arp 1.9.6
template and a project name
Choose the project name carefully as this is reflected
in directories, namespaces, project names, etc.

42. Your First S#arp Solution
Open the solution, and under the
CrudScaffolding or
CrudScaffoldingForEnterpriseApp project open
the ScaffoldingGeneratorCommand T4
Setup the object name and properties for the
Domain object you want to create
Set the ScaffoldingGenerator path to reflect the
root of your solution
Uncomment the generator.Run() statement,
save the T4, and recomment the
generator.Run()

43. Your First S#arp Solution
Modify the DB connection string in the
$SolutionName$.Web project, NHibernate.config
file
Create the corresponding table in the app DB for
the object you created earlier, adding an int Id
column
Create a DB table called hibernate_unique_key
with a single bigint column named next_hi –
insert one row with a starting value of 1 – this is
the seed used for int Id columns

44. Bugs
Modify this line in
$SolutionName$.WebCastleWindsorCompone
ntRegistrar.cs:
container.Register(Component.For(typeof(
IValidator))
.ImplementedBy(typeof(Validator))
.Named("validator"));
To read:
container.Register(Component.For(typeof(SharpArch.
Core.CommonValidator.IValidator))
.ImplementedBy(typeof(Validator))
.Named("validator"));

45. Bugs
Comment out this line in Application_Start of
Global.asax.cs:
ModelValidatorProviders.Providers.Add(new
NHibernateValidatorProvider());

46. Demo

47. Let’s Do This Ourselves
Well, with help from
Tony Sneed
http://blog.tonysneed.co
m/2011/10/08/peeling-
back-the-onion-
architecture/

48. Resources
Jeffery Palermo’s Blog
http://jeffreypalermo.com/
http://jeffreypalermo.com/blog/the-onion-architecture-part-1/
S#arp Architecture Framework
http://www.sharparchitecture.net/
https://github.com/sharparchitecture/sharp-architecture/
Domain-Driven Design
http://domaindrivendesign.org/
http://www.infoq.com/minibooks/domain-driven-design-quickly
Other
www.Centare.com
blog.GaryPedretti.com – my blog

49. Thank You!!
Gary.Pedretti@Centare.com