Code to DI For - Dependency Injection for Modern Applications

http://slideshare.net/CalebJenkins

“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

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

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

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

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

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

{
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

{
private ISpyGadget spyWatch;
private IMission stopDrEvil;
{
spyWatch = new SpyWatch();
stopDrEvil = new StopDrEvilMission();
}
{
spyWatch.UseTo(stopDrEvil);
}
}
Interfaces
=
Looser Coupling

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

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

{
{
}
public DoubleOSuperSpy (ISecretMission Mission,
ISpyGadget Gadget)
{
mission = Mission;
gadget = Gadget;
}
public ISpyGadget Gadget
{
set { gadget = Value; }
}
public void SetMission(ISecretMission Mission)
{
mission = Mission;
}
{
gadget.UseGadget(mission);
}
public void UseGadget(ISecretMission Mission)
Factory Dependency
Dependency Injection

{
{
}
ISpyGadget Gadget)
{
mission = Mission;
gadget = Gadget;
}
public ISpyGadet Gadget
{
}
{
mission = Mission;
}
public void UseWeapon(ISecretMission Mission)
{
gadget.UserGadget(Mission);
}

{
{
}
ISpyGadget Gadget)
{
mission = Mission;
gadget = Gadget;
}
public ISpyGadget Gadget
{
}
{
mission = Mission;
}
{
}
public void RunMission (ISecretMission Mission)
{
gadget.UseGadget(Mission);
}

{
private DoubleOSuperSpy()
{
}
ISpyGadget Gadget)
{
mission = Mission;
gadget = Gadget;
}
{
}
}

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

{
{
ISpyGadget gadget = new SpyWatch();
ISecretMission mission = new StopDrEvilMission();
ISecretAgent agent = new DoubleOSuperSpy(gadget);
agent.RunMission(mission);
}
}
Manual

Factory
ISpyGadget
ISecretMission
ISecretAgent
MyApplication
Factory
ISpyGadget
ISecretMission

{
{
ISecretAGent agent = Factory.GetSecretAgent();
ISpyGadget gadget = Factory.GetSpyGadget();
ISecretMission mission = Factory.GetSecretMission();
// Manual Dependency Injection
agent.SetMission(mission);
agent.SetSpyGadget(gadget);
agent.RunMission();
}
}
Manual

Manual
{
{
ISecretAgent agent =
(ISecretAgent) Context.GetInstance(“ISecretAgent”);
}
}
Frameworks

Manual
{
{
(ISecretAgent) Context.GetInstance(“ISecretAgent”);
}
}
Frameworks
{
{
Context.GetInstance<ISecretAgent>();
}
}
(with Generics)

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

<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>
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

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>();
}
}

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>
Implementation Mapping
Simple Property Injection
Property Injection
Constructor Injection
Instantiation Model:
Singelton
Transient
Pool
Interceptors / Listeners
Per Thread
Generics

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

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

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

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

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)

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

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

Common Service Locator
commonservicelocator.codeplex.com

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

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

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

Code to DI For - Dependency Injection for Modern Applications

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