This talk introduces the concepts of factories, strategy pattern, Inversion of Control, dependency injection and several of the available frameworks. We'll also look at common dependency injection patterns and various IoC/DI frameworks, the pros & cons, practical steps and guidance as well some of the real world scenarios with impact to unit testing and application architecture. First presented at the Ft. Worth .NET Users Group on March 15th, 2016 - http://developingux.com/2016/03/14/code-to-di-for-in-ft-worth/ - Code will be posted to my GitHub soon! https://github.com/calebjenkins/ (Talks.Code-to-DI-For)

4. http://slideshare.net/CalebJenkins

6. “The single greatest thing that you can do to make your
code more testable and healthy is to start taking a
Dependency Injection approach to writing software”
- Real World .NET, C# and Silverlight
Wrox Press 2012
Caleb Jenkins

10. Super Spy
(saves the world)
Dr. Evil
(bad guy)

11. public class DoubleOSuperSpy
{
public void StopDrEvilWithSpyWatch()
{
// Stop Dr. Evil
}
}

12. but what if we wanted to
rescue the queen
use our spy car
stop nuclear attack,

13. ?

14. ?

15. ?

16. public class DoubleOSuperSpy
{
public void StopDrEvilWithSpyWatch()
{
// Stop Dr. Evil
}
public void StopDrEvilWithSpyCar()
{
}
public void SaveQueenWithSecretCrocodile()
{
}
// Etc...
}

18. public interface ISecretAgent
{
void RunMission(ISecretMission Mission);
}
public interface ISpyGadget
{
void UseGadget(string Target);
} public interface ISecretMission
{
}
public class SpyWatch : ISpyGadget
public class StopDrEvilMission : ISecretMission
public class DoubleOSuperSpy : ISecretAgent

19. public class DoubleOSuperSpy : ISecretAgent
{
private ISpyGadget spyWatch;
private IMission stopDrEvil;
public DoubleOSuperSpy()
{
spyWatch = new SpyWatch();
stopDrEvil = new StopDrEvilMission();
}
public void RunMission()
{
spyWatch.UseTo(stopDrEvil);
}
}
Separation of Concerns
+
Grouping of Features
=
Strategy Pattern

20. public class DoubleOSuperSpy : ISecretAgent
{
private ISpyGadget spyWatch;
private IMission stopDrEvil;
public DoubleOSuperSpy()
{
spyWatch = new SpyWatch();
stopDrEvil = new StopDrEvilMission();
}
public void RunMission()
{
spyWatch.UseTo(stopDrEvil);
}
}
Interfaces
=
Looser Coupling

21. public class Factory
{
public static ISecretAgent GetSecretAgent()
{
// Check config
return new DoubleOSuperSpy();
}
public static ISecretGadget GetSpyGadget()
{
// Check config
return new SpyWatch();
}
public static ISecretMission GetSecretMission()
{
// Check Config
return new StopDrEvilMission();
}
}
A Factory

22. Factory Pattern

23. public class DoubleOSuperSpy : ISecretAgent
{
private ISpyGadget gadget;
private ISecretMission mission;
public DoubleOSuperSpy()
{
gadget = Factory.GetSpyGadget();
mission = Factory.GetSecretMission();
}
public void UseGadget()
{
gadget.UserGadget(mission);
}
}
Abstract Factory Pattern
=
Abstraction of Creation
+
Polymorphism

24. public class DoubleOSuperSpy : ISecretAgent
{
private ISpyGadget gadget;
private ISecretMission mission;
public DoubleOSuperSpy()
{
gadget = Factory.GetSpyGadget();
mission = Factory.GetSecretMission();
}
public DoubleOSuperSpy (ISecretMission Mission,
ISpyGadget Gadget)
{
mission = Mission;
gadget = Gadget;
}
public ISpyGadget Gadget
{
set { gadget = Value; }
}
public void SetMission(ISecretMission Mission)
{
mission = Mission;
}
public void UseGadget()
{
gadget.UseGadget(mission);
}
public void UseGadget(ISecretMission Mission)
Factory Dependency
Dependency Injection

25. public class DoubleOSuperSpy : ISecretAgent
{
private ISpyGadget gadget;
private ISecretMission mission;
public DoubleOSuperSpy()
{
gadget = Factory.GetSpyGadget();
mission = Factory.GetSecretMission();
}
public DoubleOSuperSpy (ISecretMission Mission,
ISpyGadget Gadget)
{
mission = Mission;
gadget = Gadget;
}
public ISpyGadet Gadget
{
set { gadget = Value; }
}
public void SetMission(ISecretMission Mission)
{
mission = Mission;
}
public void UseWeapon(ISecretMission Mission)
{
gadget.UserGadget(Mission);
}
public void UseGadget()

26. public class DoubleOSuperSpy : ISecretAgent
{
private ISpyGadget gadget;
private ISecretMission mission;
public DoubleOSuperSpy()
{
gadget = Factory.GetSpyGadget();
mission = Factory.GetSecretMission();
}
public DoubleOSuperSpy (ISecretMission Mission,
ISpyGadget Gadget)
{
mission = Mission;
gadget = Gadget;
}
public ISpyGadget Gadget
{
set { gadget = Value; }
}
public void SetMission(ISecretMission Mission)
{
mission = Mission;
}
public void RunMission()
{
gadget.UseGadget(mission);
}
public void RunMission (ISecretMission Mission)
{
gadget.UseGadget(Mission);
}

27. public class DoubleOSuperSpy : ISecretAgent
{
private ISpyGadget gadget;
private ISecretMission mission;
private DoubleOSuperSpy()
{
}
public DoubleOSuperSpy (ISecretMission Mission,
ISpyGadget Gadget)
{
mission = Mission;
gadget = Gadget;
}
public void RunMission()
{
gadget.UseGadget(mission);
}
}

28. public class MyApplication
{
public void static Main()
{
ISecretAgent agent = Factory.GetSecretAgent();
ISpyGadget gadget = Factory.GetSpyGadget();
ISecretMission mission = Factory.GetSecretMission();
// Manual Dependency Injection
agent.SetMission(mission);
agent.SetGadget(gadget);
agent.RunMissionMission();
}
}
Manual
Dependency Injection

29. public class MyApplication
{
public void static Main()
{
ISpyGadget gadget = new SpyWatch();
ISecretMission mission = new StopDrEvilMission();
ISecretAgent agent = new DoubleOSuperSpy(gadget);
agent.RunMission(mission);
}
}
Manual
Dependency Injection

32. Factory
ISpyGadget
ISecretMission
ISecretAgent
MyApplication
Factory
ISpyGadget
ISecretMission

33. public class MyApplication
{
public void static Main()
{
ISecretAGent agent = Factory.GetSecretAgent();
ISpyGadget gadget = Factory.GetSpyGadget();
ISecretMission mission = Factory.GetSecretMission();
// Manual Dependency Injection
agent.SetMission(mission);
agent.SetSpyGadget(gadget);
agent.RunMission();
}
}
Manual
Dependency Injection

34. Manual
Dependency Injection
public class MyApplication
{
public void static Main()
{
ISecretAgent agent =
(ISecretAgent) Context.GetInstance(“ISecretAgent”);
}
}
Dependency Injection
Frameworks

35. Manual
Dependency Injection
public class MyApplication
{
public void static Main()
{
ISecretAgent agent =
(ISecretAgent) Context.GetInstance(“ISecretAgent”);
}
}
Dependency Injection
Frameworks
public class MyApplication
{
public void static Main()
{
ISecretAgent agent =
Context.GetInstance<ISecretAgent>();
}
}
Dependency Injection
(with Generics)

36. castleproject.org
springframework.net
ninject.org
unity.codeplex.com structuremap.github.io
simpleinjector.org
autofac.org

37. <factoryconfig type="Improving.ProviderFactory, ProviderFactory">
<factories>
<factory interface=“ISpyGadget" assembly=“Acme.MI6" class=“LaserSpyWatch“ />
<factory interface=“ISecretAgent" assembly=“Acme.MI6" class=“DoubleOSuperSpy”>
<params>
<param name=“Name" value=“Bond, James” type="System.String"/>
</params>
</factory>
<factory interface=“ISecretMission" assembly=“Acme.MI6" class=“StopDrEvilMission“
lifespan=“singleton”>
</factory>
</factories>
</factoryconfig>
Dependency Injection
Configuration Concepts
* Note: This is a conceptual configuration and not specific to any
IoC / di framework. Some IoC’s don’t use config, like Ninject that
relies on special [attributes] for mappings

38. public class DependencyConfigModule : StandardModule
{
public override void Load()
{
// Factory
Bind<IFactory>().To<factory>().Using<SingletonBehavior>();
// Models
Bind<ISecretAgent>().To<DoubleOSuperSpy>().Using<TransientBehavior>();
Bind<ISecretMission>().To<StopDrEvilMission>().Using<TransientBehavior>();
Bind<ISpyGadget>().To<LaserSpyWatch>().Using<TransientBehavior>();
}
}
Dependency Injection
Configuration Concepts
* Note: This is a conceptual configuration and not specific to any
IoC / di framework. Some IoC’s don’t use config, like Ninject that
relies on special [attributes] for mappings

39. public class DependencyConfigModule : StandardModule
{
public override void Load()
{
// Factory
Bind<IFactory>().To<factory>().Using<SingletonBehavior>();
// Models
Bind<ISecretAgent>().To<DoubleOSuperSpy>().Using<TransientBehavior>();
Bind<ISecretMission>().To<StopDrEvilMission>().Using<TransientBehavior>();
Bind<ISpyGadget>().To<LaserSpyWatch>().Using<TransientBehavior>();
}
}
<factoryconfig type="Improving.ProviderFactory, ProviderFactory">
<factories>
<factory interface=“ISpyGadget" assembly=“Acme.MI6" class=“LaserSpyWatch“ />
<factory interface=“ISecretAgent" assembly=“Acme.MI6" class=“DoubleOSuperSpy”>
<params>
<param name=“Name" value=“Bond, James” type="System.String"/>
</params>
</factory>
<factory interface=“ISecretMission" assembly=“Acme.MI6" class=“StopDrEvilMission“
lifespan=“singleton”>
</factory>
</factories>
</factoryconfig>
Dependency Injection
Configuration Concepts
Implementation Mapping
Simple Property Injection
Property Injection
Constructor Injection
Instantiation Model:
Singelton
Transient
Pool
* Note: This is a conceptual configuration and not specific to any
IoC / di framework. Some IoC’s don’t use config, like Ninject that
relies on special [attributes] for mappings
Interceptors / Listeners
Per Thread
Generics

40. LET’S LOOK AT
SOME CODE…

41. Interceptors and
Listeners

42. Interceptors and
Listeners

43. The mission has begun
Dr. Evil has been stopped!
It took :22 seconds!
Interceptors and Listeners

44. Stop Dr. Evil
Dynamic Proxy
Security must be
licensed to kill
(007)
Logging Bond is
about to begin
mission
Interceptors and Listeners (AOP)
Multi-Threading
Invoke UI Thread

45. Longest running “complete stack”
Windsor Container
Dynamic Proxy
Active Record (nHibernate)
ASP.NET Mono Rail
Visual Studio Tooling
Well Established Community
Integrates with ASP.NET MVC
ASP.NET | Sharepoint
Winforms | WPF | WCF | WF |
Console Apps
castleproject.org

46. springframework.net
“Spring Framework” is THE way to
do JAVA development
Spring .NET is the .NET equivalent
Nice bridge for Java Spring
developers moving to .NET
Interface 21

47. ninject.org
DI “gateway drug”
Light weight / super fast to configure
DI (Integrates with Castle for IoC / AOP)
.NET
Silverlight
Windows Mobile/Phone
No XML Config
(Fluent Config)

48. unity.codeplex.com
github.com/unitycontainer/unity
From Microsoft
Integration with other Application Blocks
Microsoft Support
Now Maintained by the community (OSS)

49. castleproject.org
springframework.net
ninject.org
unity.codeplex.com structuremap.github.io
simpleinjector.org
autofac.org

50. commonservicelocator.codeplex.com
IMPLEMENTATION
Castle Windsor Adapter
Spring .NET Adapter
Unity Adapter
StructureMap Adapter
Autofac Adapter
MEF Adapter now on .NET Framework 4.0
LinFu Adapter
Multi-target CSL binaries
Service Locator Adapter
Implementations

51. Common Service Locator
commonservicelocator.codeplex.com

52. Common Service Locator
commonservicelocator.codeplex.com

53. POOR MAN’S DIpublic class SuperSpyLib
{
private ISecretAgent agent;
private ISpyGadget gadget;
private ISecretMission mission;
public void SuperSpyLib (ISecretAgent Agent,
ISpyGadget Gadget, ISecretMission Mission)
{
agent = Agent;
gadget = Gadget;
mission = Mission;
}
}

54. POOR MAN’S DIpublic class SuperSpyLib
{
private ISecretAgent agent;
private ISpyGadget gadget;
private ISecretMission mission;
public void SuperSpyLib (ISecretAgent Agent,
ISpyGadget Gadget, ISecretMission Mission)
{
agent = Agent;
gadget = Gadget;
mission = Mission;
}
}

55. POOR MAN’S DIpublic class SuperSpyLib
{
private ISecretAgent agent;
private ISpyGadget gadget;
private ISecretMission mission;
public void SuperSpyLib (ISecretAgent Agent,
ISpyGadget Gadget, ISecretMission Mission)
{
agent = Agent;
gadget = Gadget;
mission = Mission;
}
}
public class SuperSpyLib
{
private ISecretAgent agent;
private ISpyGadget gadget;
private ISecretMission mission;
public void SuperSpyLib (ISecretAgent Agent,
ISpyGadget Gadget, ISecretMission Mission)
{
agent = Agent;
gadget = Gadget;
mission = Mission;
}
}
public void SuperSpyLib ()
: this (new SuperAgent(),
new SpyAgent(), new StopDrEvilMission())
{
// Default Constructor – Poor Man’s DI
}

56. POOR MAN’S DIpublic class SuperSpyLib
{
private ISecretAgent agent;
private ISpyGadget gadget;
private ISecretMission mission;
public void SuperSpyLib (ISecretAgent Agent,
ISpyGadget Gadget, ISecretMission Mission)
{
agent = Agent;
gadget = Gadget;
mission = Mission;
}
}
public class SuperSpyLib
{
private ISecretAgent agent;
private ISpyGadget gadget;
private ISecretMission mission;
public void SuperSpyLib (ISecretAgent Agent,
ISpyGadget Gadget, ISecretMission Mission)
{
agent = Agent;
gadget = Gadget;
mission = Mission;
}
}
public void SuperSpyLib ()
: this (new SuperAgent(),
new SpyAgent(), new StopDrEvilMission())
{
// Default Constructor – Poor Man’s DI
}

57. POOR MAN’S DIpublic class SuperSpyLib
{
private ISecretAgent agent;
private ISpyGadget gadget;
private ISecretMission mission;
public void SuperSpyLib (ISecretAgent Agent,
ISpyGadget Gadget, ISecretMission Mission)
{
agent = Agent;
gadget = Gadget;
mission = Mission;
}
}
public class SuperSpyLib
{
private ISecretAgent agent;
private ISpyGadget gadget;
private ISecretMission mission;
public void SuperSpyLib (ISecretAgent Agent,
ISpyGadget Gadget, ISecretMission Mission)
{
agent = Agent;
gadget = Gadget;
mission = Mission;
}
}
public void SuperSpyLib ()
: this (new SuperAgent(),
new SpyAgent(), new StopDrEvilMission())
{
// Default Constructor – Poor Man’s DI
}

64. developingUX.com
speakerpedia.com/speakers/caleb-jenkins
@calebjenkins

65. speakerpedia.com/prog
rammers

67. developingUX.com
speakerpedia.com/speakers/caleb-jenkins
@calebjenkins