I am trying to understand TDD more and all the examples I have seen regarding DI have been classes/interfaces that only have methods on them eg.
public interface IUserRepository
{
User GetByID(int ID);
}
public class UserRepo : IUserRepository
{
private IUserRepository Repo;
public UserRepo(IUserRepository repo)
{
this.Repo. = repo;
}
public User GetByID(int ID) {}
}
.....
private void SetupDI()
{
container.Register<IUserRepository>.With(UserRepository);
}
I recently started writing an interface with properties on it and stopped as was unsure how this would be accomplished.
Is having properties in interfaces OK in terms of DI? Is it good design?
I would assume that these properties would be injected like so:
private void SetupDI()
{
var myStringProp = GetPropValue("MyStringProp");
var myIntProp = GetPropValue("MyIntProp");
container.Register<IUserRepository>.With
(
new UserRepository() {
StringProperty = myStringProp;
IntProperty = myIntProp;
}
);
}
OR
Would you pass all the required properties in the constructor:
private void SetupDI()
{
var myStringProp = GetPropValue("MyStringProp");
var myIntProp = GetPropValue("MyIntProp");
container.Register<IUserRepository>.With
(
new UserRepository(myStringProp,myIntProp)
);
}
It's perfectly fine to use properties in interfaces, but your question is really mainly about constructor vs. property injection and not so much about using properties in interfaces.
The former (constructor injection) is clearly preferred since the dependencies of a class must be passed in at the time of creation, so they are clearly visible and not "hidden". Personally I aim to always use constructor injection, and property injection only as a last resort, e.g. when there is a cyclic dependency that otherwise cannot be resolved (at that time it is probably better to rethink the design).
I personally inject dependencies into the constructor and store them as private members. often, i will find myself with two constructors, one default that is most commonly used by the application, and one that takes the dependencies as parameters. I have found this helps me in unit testing but also gives me the flexibility.
Related
I am trying to get IoC working with Unity in C# with the idea of a passing a wrapper/composite class into the children.
The top level class that composes multiple classes provides some common functionality that the composed classes require access to.
To illustrate:
// The top composite class
public class Context : IContext {
public ISomething SomethingProcessor { get; }
public IAnother AnotherProcessor { get; }
public Context(ISomething something, IAnother another) {
this.SomethingProcessor = something;
this.AnotherProcessor = processor;
}
// A function that individual classes need access to, which itself calls one of the children.
public string GetCommonData() {
return this.AnotherProcessor.GetMyData();
}
}
public class Something : ISomething {
private _wrapper;
public Something(IContext context) {
this._wrapper = context;
}
// This class has no knowledge of IAnother, and requests data from the master/top class, which knows where to look for whatever.
public void Do() {
Console.WriteLine(_wrapper.GetCommonData());
}
}
public class Another : IAnother {
public string GetMyData() {
return "Foo";
}
}
If you didn't use IoC, it's easy, as the constructor for the Context class becomes:
public Context() {
this.SomethingProcessor = new Processor(this);
this.AnotherProcessor = new Another();
}
But when you're using IoC, the idea of "this" doesn't exist yet because it is yet to be constructed by the injector. Instead what you have a is a circular dependency.
container.RegisterType<ISomething, Something>();
container.RegisterType<IAnother, Another>();
container.RegisterType<IContext, Context>();
var cxt = container.Resolve<IContext>(); // StackOverflowException
The above example has been greatly simplified to illustrate the concept. I'm struggling to find the "best practice" way of dealing with this kind of structure to enable IOC.
Factory pattern is a way construct an object based on other dependencies or logical choices.
Factory Method: "Define an interface for creating an object, but let
the classes which implement the interface decide which class to
instantiate. The Factory method lets a class defer instantiation to
subclasses" (c) GoF.
Lots of construction.. hence the name Factory Pattern
A crude code sample that could be used with DI
public class ContextFactory : IContextFactory {
_anotherProcessor = anotherProcessor;
public ContextFactory(IAnotherProcessor anotherProcessor) {
//you can leverage DI here to get dependancies
}
public IContext Create(){
Context factoryCreatedContext = new Context();
factoryCreatedContext.SomethingProcessor = new SomethingProcessor(factoryCreatedContext )
factoryCreatedContext.AnotherProcessor = _anotherProcessor;
//You can even decide here to use other implementation based on some dependencies. Useful for things like feature flags.. etc.
return context;
}
}
You can get away with this, maybe? - but there is still the cyclic reference issue here and I would never commit this kind of code.
The problem here you need to concentrate on Inversion Of Control of that GetCommonData
Your SomethingProcessor should not rely on methods in another class. This is where In Inheritance could be used but Inheritance can become very complicated very quickly.
The best way forward is to Identify the ONE thing that is needed by both or many other places and break that out into a new Dependency. That is how you Invert Control.
TIP:
Don't overdo Interfaces- Use Interfaces where you think you will be working with Polymorphism, such as a collection of different objects that must promise you they have implemented a specific method/property. Otherwise you are over using Interfaces and increasing complexity. DI doesn't have to use Interfaces it can be a concrete implementation. Interfaces on Repositories are a good use since you can switch Databases out easily but Interfaces a factory like this is not really needed.
I don't know the name of this pattern, or even if it is a bad or good practice, but you can solve your problem of "double-binding" by creating a method to bind the "IContext", instead of doing it in the constructor.
For instance,
1) ISomething has a void BindContext(IContext context) method
2) You implement it as such :
class Something : ISomething
{
IContext _wrapper;
// ... nothing in constructor
public void BindContext(IContext context)
{
_wrapper = context;
}
}
3) Remove the IContext dependency injection in Something constructor.
And you call it from the context constructor :
public Context(ISomething something, IAnother another) {
this.SomethingProcessor = something;
this.SomethingProcessor.BindContext(this);
// same for IAnother
}
And you do the same for IAnother. You could even extract some common interface "IBindContext" to make things a beat more "DRY" (Don't Repeat yourself) and make IAnother and ISomething inherit from it.
Not tested, and again : not sure it's the best way to do such dependency design. I'll be glad if there is another answer which gives a state-of-the-art insight about this.
Hi this might be trivial but I am trying to understand the class instantiation using interface. So below is my code:
public interface IRepository
{
string GetMemberDisplayName();
}
public class Repository : IRepository
{
private readonly Manager _manager;
public Repository() {}
public Repository(string connectionName)
{
_manager = new Manager(connectionName);
}
public string GetMemberDisplayName(string ID)
{
return "FooFoo";
}
}
Now in another class that uses the repository class functionality has instantiated it as follows:
public class LogServiceHelper
{
readonly IRepository _alrAttendance;
readonly IRepository _alrUsers;
public LogServiceHelper()
{
_alrAttendance = new Repository("value1");
_alrUsers = new Repository("value2");
}
public string GetMemberName(string empId)
{
return _alrUsers.GetMemberDisplayName(empId);
}
}
My question is if this is correct way to instantiate a class with parameterized constructor. And if yes, then second question is why do we need interface in this case. We could directly instantiate the class without creating the interface?
Yes, that's how to invoke a parameterized constructor, but no, that's not what you should be doing.
As you have it, LogServiceHelper has a hard dependency on the Repository class, and so you are right, the interfaces don't buy you anything. However, if they were injected:
public LogServiceHelper(IRepository attendanceRepo, IRepository userRepo)
{
_alrAttendance = attendanceRepo;
_alrUsers = userRepo;
}
You suddenly gain the benefits of abstraction. Notably that a unit test could pass in fake repositories, and that you can switch to another implementation of IRepository without changing LogServiceHelper.
The next question is then "Who creates the Repository concrete class?". For that, I refer you to the variety of DI/IoC containers out there, such as Autofac, Unity, and NInject.
We could directly instantiate the class without creating the
interface?
This is indeed true and it might work without any problem. But then we are coming to the crucial questions:
Is my code testable, how would I test this piece of code?
Could I easily change the behavior without changing LogServiceHelper
If you don't rely on the abstraction, the answer to the above questions is unfortunately, no. Luckily there is something called SOLID and the D stands for Dependency Injection Principle.
public LogServiceHelper(IRepository alrAttendance, IRepository alrUsers)
{
_alrAttendance = alrAttendance;
_alrUsers = alrUsers;
}
So, with this simple change, you made decoupling of the moduls and all of a sudden you are relying on the abstraction which gains a lot of benefits to design.
Background / Goal
We have several "client sites" on our web app that users can switch between
We do a lot of wiring up of objects based on factories that take in the client site ID and create an instance
I would like to inject these dependencies into the classes instead
I also want to make sure I can pass in my own implementations to the constructor for the purposes of unit testing.
We have initially elected to use StructureMap 3.x to do so, but are open to alternatives if they can help us solve this scenario gracefully.
Question
In instances where I require a different dependency based on a client site ID that I'll only get at run-time, what is the appropriate way to set up an IoC container and the appropriate way to request the object from it in order to make it as painless as possible?
Am I thinking about this wrong and unintentionally creating some sort of anti-pattern?
Example Code
Normally we're doing something like the following coming in:
public class MyService
{ DependentObject _dependentObject;
public MyService(int clientSiteID)
{
// ...
_dependentObject = new dependentObjectFactory(clientSiteID).GetDependentObject();
}
public void DoAThing()
{
//...
_dependentObject.DoSomething();
}
}
What I'd like to do:
public class MyService
{ DependentObject _dependentObject;
public MyService(int clientSiteID)
{
// ...
_dependentObject = MyTypeResolver.GetWIthClientContext<IDependentObject>(clientSiteID);
}
public MyService(int clientSiteID, IDependentObject dependentObject)
{
// ...
_dependentObject = dependentObject;
}
public void DoAThing()
{
//...
_dependentObject.DoSomething();
}
}
I would set up the IoC container in such a way that I can use my MyTypeResolver to pass in the clientSiteID, and have the container call my DependentObjectFactory and return the correct object result.
I'm new to IoC containers, and while I'm trying to plow through the literature, I have the feeling it may be easier than I'm making it so I'm asking here.
Probably the simplest way to do this is to use an Abstract Factory. Most IOC frameworks can auto-create them for you, but here's how you can do it manually (I always prefer to do it manually first so I know it works, and then you can check out how the framework can help you automagic it)
Now one thing to mention - I would recommend a slight readjustment of how the final solution works, but I'll go into that once I have shown how it can currently work. Example below assumes Ninject and please excuse any typos, etc.
First create an interface for your dependency
public interface IDependentObject
{
void DoSomething();
}
Then declare empty marker interfaces for each specific implementation of IDependentObject
public interface INormalDependentObject:IDependentObject{};
public interface ISpecialDependentObject:IDependentObject{}
and implement them:
public class NormalDependentObject:INormalDependentObject
{
readonly int _clientID;
public DependentObject(int clientID)
{
_clientID=clientID;
}
public void DoSomething(){//do something}
}
public class DependentObject:ISpecialDependentObject
{
readonly int _clientID;
public DependentObject(int clientID)
{
_clientID=clientID;
}
public void DoSomething(){//do something really special}
}
and of course as you mentioned you may have many more implementations of IDependentObject.
There may be a more elegant way of allowing your IOC framework to resolve at runtime without having to declare the marker interfaces; but for now I find it useful to use them as it makes the binding declarations easy to read :)
Next, declare an interface and implementation of an IDependentObjectFactory:
public interface IDependentObjectFactory
{
IDependentObject GetDependenObject(int clientID);
}
public class DependentObjectFactory: IDependentObjectFactory
{
readonly _kernel kernel;
public DependentObjectFactory(IKernel kernel)
{
_kernel=kernel;
}
public IDependentObject GetDependenObject(int clientID)
{
//use whatever logic here to decide what specific IDependentObject you need to use.
if (clientID==100)
{
return _kernel.Get<ISpecialDependantObject>(
new ConstructorArgument("clientID", clientID));
}
else
{
return _kernel.Get<INormalDependentObject>(
new ConstructorArgument("clientID", clientID));
}
}
}
Wire these up in your Composition Root:
_kernel.Bind<INormalDependentObject>().To<NormalDependentObject>();
_kernel.Bind<ISpecialDependentObject>().To<SpecialDependentObject>();
_kernel.Bind<IDependentObjectFactory>().To<DependentObjectFactory>();
and finally inject your factory into the service class:
public class MyService
{
IDependentObject _dependentObject;
readonly IDependentObjectFactory _factory;
//in general, when using DI, you should only have a single constructor on your injectable classes. Otherwise, you are at the mercy of the framework as to which signature it will pick if there is ever any ambiguity; most all of the common frameworks will make different decisions!
public MyService(IDependentObjectFactory factory)
{
_factory=factory;
}
public void DoAThing(int clientID)
{
var dependent _factory.GetDependentObject(clientID);
dependent.DoSomething();
}
}
Suggested changes
One immediate change from your structure above is that I have left clientID out of the service constructor and moved it to a method argument of DoAThing; this is because it makes a bit more sense to me that the Service itself would be stateless; of course depending on your scenario, you may want to not do that.
I mentioned that I had a slight adjustment to suggest , and it's this; the solution above depends (no pun!) on implementations of IDependentObject having a constructor with this signature:
public SomeDependency(int clientID)
If they don't have that signature then the factory won't work; personally I don't like my DI to have to know anything about constructor params because it takes you out of purely dealing with interfaces and forcing you to implement specific ctor signatures on your concrete classes.
It also means that you can't reliably make your IDependentObjects be part of the whole DI process (i.e whereby they themselves have dependency graphs that you want the framework to resolve) because of the forced ctor signature.
For that reason I'd recommend that IDependentObject.DoSomething() itself be changed to DoSomething(int clientID) so that you can elide the new ConstructorArgument part of the factory code; this means that your IDependentObject s can now all have totally different ctor signatures, meaning they can have different dependencies if needs be. Of course this is just my opinion, and you will know what works best in your specific scenario.
Hope that helps.
I have the IRespository registered twice (with names) in the following code:
// Setup the Client Repository
IOC.Container.RegisterType<ClientEntities>(new InjectionConstructor());
IOC.Container.RegisterType<IRepository, GenericRepository>
("Client", new InjectionConstructor(typeof(ClientEntities)));
// Setup the Customer Repository
IOC.Container.RegisterType<CustomerEntities>(new InjectionConstructor());
IOC.Container.RegisterType<IRepository, GenericRepository>
("Customer", new InjectionConstructor(typeof(CustomerEntities)));
IOC.Container.RegisterType<IClientModel, ClientModel>();
IOC.Container.RegisterType<ICustomerModel, CustomerModel>();
But then when I want to resolve this (to use the IRepository) I have to do a manual resolve like this:
public ClientModel(IUnityContainer container)
{
this.dataAccess = container.Resolve<IRepository>(Client);
.....
}
What I would like to do is to have it resolved in the constructor (just like IUnityContainer). I need some way to say which named type to resolve to.
Something like this: (NOTE: Not real code)
public ClientModel([NamedDependancy("Client")] IRepository dataAccess)
{
this.dataAccess = dataAccess;
.....
}
Is there a way to make my fake code work?
You can configure dependencies with or without names in the API, attributes, or via the config file. You didn't mention XML above, so I'll assume you're using the API.
To tell the container to resolve a named dependency, you'll need to use an InjectionParameter object. For your ClientModel example, do this:
container.RegisterType<IClientModel, ClientModel>(
new InjectionConstructor( // Explicitly specify a constructor
new ResolvedParameter<IRepository>("Client") // Resolve parameter of type IRepository using name "Client"
)
);
This tells the container "When resolving ClientModel, call the constructor that takes a single IRepository parameter. When resolving that parameter, resolve with the name 'Client' in addition to the type."
If you wanted to use attributes, your example almost works, you just need to change the attribute name:
public ClientModel([Dependency("Client")] IRepository dataAccess)
{
this.dataAccess = dataAccess;
.....
}
This is a very late response but the question still shows up in Google.
So anyways, 5 years later...
I have a pretty simple approach. Usually when you need to use "named dependency" it's because you're trying to implement some kind of strategy pattern. In that case, I simply create a level of indirection between Unity and the rest of my code called the StrategyResolver to not be directly depending on Unity.
public class StrategyResolver : IStrategyResolver
{
private IUnityContainer container;
public StrategyResolver(IUnityContainer unityContainer)
{
this.container = unityContainer;
}
public T Resolve<T>(string namedStrategy)
{
return this.container.Resolve<T>(namedStrategy);
}
}
Usage:
public class SomeClass: ISomeInterface
{
private IStrategyResolver strategyResolver;
public SomeClass(IStrategyResolver stratResolver)
{
this.strategyResolver = stratResolver;
}
public void Process(SomeDto dto)
{
IActionHandler actionHanlder = this.strategyResolver.Resolve<IActionHandler>(dto.SomeProperty);
actionHanlder.Handle(dto);
}
}
Registration:
container.RegisterType<IActionHandler, ActionOne>("One");
container.RegisterType<IActionHandler, ActionTwo>("Two");
container.RegisterType<IStrategyResolver, StrategyResolver>();
container.RegisterType<ISomeInterface, SomeClass>();
Now, the nice thing about this is that I will never have to touch the StrategyResolver ever again when adding new strategies in the future.
It's very simple. Very clean and I kept the dependency on Unity to a strict minimum. The only time I would have touch the StrategyResolver is if I decide to change container technology which is very unlikely to happen.
Hope this helps!
Edit: I don't really like the accepted answer because when you use the Dependency attribute in your service's constructor you actually have a hard dependency on Unity. The Dependency attribute is part of the Unity library. At that point you might as well pass an IUnityContainer dependency everywhere.
I prefer having my service classes depend on objects that I completely own instead of having a hard dependency on an external library all over the place. Also using Dependency attribute makes the constructors signatures less clean and simple.
Furthermore, this technique allows to resolve named dependencies at runtime without having to hardcode the named dependencies in the constructor, in the application configuration file or use InjectionParameter which are all methods that require to know what named dependency to use at design time.
Edit (2016-09-19):
For those that might wonder, the container will know to pass itself when you are requesting IUnityContainer as dependency, as shown in the StrategyResolver constructor signature.
Edit (2018-10-20):
Here's another way, simply using a factory:
public class SomeStrategyFactory : ISomeStrategyFactory
{
private IStrategy _stratA;
private IStrategy _stratB;
public SomeFactory(IStrategyA stratA, IStrategyB stratB)
{
_stratA = stratA;
_stratB = stratB;
}
public IStrategy GetStrategy(string namedStrategy){
if (namedStrategy == "A") return _stratA;
if (namedStrategy == "B") return _stratB;
}
}
public interface IStrategy {
void Execute();
}
public interface IStrategyA : IStrategy {}
public interface IStrategyB : IStrategy {}
public class StrategyA : IStrategyA {
public void Execute(){}
}
public class StrategyB : IStrategyB {
public void Execute() {}
}
Usage:
public class SomeClass : ISomeClass
{
public SomeClass(ISomeStrategyFactory strategyFactory){
IStrategy strat = strategyFactory.GetStrategy("HelloStrategy");
strat.Execute();
}
}
Registration:
container.RegisterType<ISomeStrategyFactory, SomeStrategyFactory>();
container.RegisterType<IStrategyA, StrategyA>();
container.RegisterType<IStrategyB, StrategyB>();
container.RegisterType<ISomeClass, SomeClass>();
This 2nd suggestion is the same thing but using the factory design pattern.
Hope this helps!
You should be able to use ParameterOverrides
var repository = IOC.Container.Resolve<IRepository>("Client");
var clientModel = IOC.Container.Resolve<ClientModel>(new ParameterOverrides<ClientModel> { {"dataAccess", repository } } );
edit:
I'm not sure why you're passing around the UnityContainer - personally, we inject our dependencies into the constructor themselves (which is "normal" from what I've seen). But regardless, you can specify a name in your RegisterType and Resolve methods.
IOC.Container.RegisterType<IRepository, GenericRepository>("Client");
IOC.Container.Resolve<IRepository>("Client");
and it will give you the type you registered for that name.
Don't do this - just create a class ClientRepository : GenericRepository { } and utilise the Type system.
I have a wcf service and on the client i have:
var service = new ServiceReference1.CACSServiceClient()
The actual service code is:
public CACSService() : this(new UserRepository(), new BusinessRepository()) { }
public CACSService(IUserRepository Repository, IBusinessRepository businessRepository)
{
_IRepository = Repository;
_IBusinessRepository = businessRepository;
}
So, all this works fine, but i don't like how i am newing up all the repositories at the same time because the client code might not need to new up the UserRepository and only interested in newing up the BusinessRepository. So, is there a way to pass in something to this code:
var service = new ServiceReference1.CACSServiceClient()
to tell it which repository to new up based on the code that is calling the service or any other advice i need to go about when designing the repositories for my entity framework. Thankx
The beauty of pure DI is that you shouldn't worry about the lifetimes of your dependencies, because these are managed for you by whoever supply them (a DI Container, or some other code you wrote yourself).
(As an aside, you should get rid of your current Bastard Injection constructors. Throw away the parameterless constructor and keep the one that explicitly advertises its dependencies.)
Keep your constructor like this, and use _IRepository and _IBusinessRepository as needed:
public CACSService(IUserRepository Repository, IBusinessRepository businessRepository)
{
_IRepository = Repository;
_IBusinessRepository = businessRepository;
}
If you worry that one of these repositories are not going to be needed at run-time, you can inject a lazy-loading implementation of, say, IUserRepsository instead of the real one you originally had in mind.
Let's assume that IUserRepository looks like this:
public interface IUserRepository
{
IUser SelectUser(int userId);
}
You can now implement a lazy-loading implementation like this:
public class LazyUserRepository : IUserRepository
{
private IUserRepository uRep;
public IUser SelectUser(int userId)
{
if (this.uRep == null)
{
this.uRep = new UserRepository();
}
return this.uRep.SelectUser(userId);
}
}
When you create CACService, you can do so by injecting LazyUserRepository into it, which ensures that the real UserRepository is only going to be initialized if it's needed.
The beauty of this approach is that you don't have to do this until you need it. Often, this really won't be necessary so it's nice to be able to defer such optimizations until they are actually necessary.
I first described the technique of Lazy Dependencies here and here.
Instead of instantiating ("newing up") the repositories on construction, you could lazy load them in their properties. This would allow you to keep your second constructor, but have your first constructor do nothing.
The user could then assign these, as needed, otherwise.
For example:
public class CACSService
{
public CACSService() {}
public CACSService(IUserRepository Repository, IBusinessRepository businessRepository)
{
_IRepository = Repository;
_IBusinessRepository = businessRepository;
}
private IUserRepository _IRepository;
public IUserRepository Repository
{
get {
if (this._IRepository == null)
this._IRepository = new UserRepository();
return this._IRepository;
}
}
// Add same for IBusinessRepository
}
Do your repositories have object-level state? Probably not, so create them as singletons and have a DI container provide them to CACService.
Otherwise, are they actually expensive to create? If not, creating a new one per request has negligible cost compared to the RPC and database operations.
Using the Ninject dependency injection container, your CACService might look like the following. Other DI containers have equally succinct mechanisms of doing this.
public class CACSService
{
public CACService
{
// need to do this since WCF creates us
KernelContainer.Inject( this );
}
[Inject]
public IUserRepository Repository
{ set; get; }
[Inject]
public IBusinessRepository BusinessRepository
{ set; get; }
}
And during your application startup, you would tell Ninject about these types.
Bind<IUserRepository>().To<UserRepository>().InSingletonScope();
Bind<IBusinessRepository>().To<BusinessRepository>().InSingletonScope();
Preface: This is a general guide to dependency inversion. If you need the default constructor to do the work (e.g. if it is new'ed up by reflection or something else), then it'll be harder to do this cleanly.
If you want to make your application configurable, it means being able to vary how your object graph is constructed. In really simple terms, if you want to vary an implementation of something (e.g. sometimes you want an instance of UserRepository, other times you want an instance of MemoryUserRepository), then the type that uses the implementation (CACService in this case) should not be charged with newing it up. Each use of new binds you to a specific implementation. Misko has written some nice articles about this point.
The dependency inversion principle is often called "parametrise from above", as each concrete type receives its (already instantiated) dependencies from the caller.
To put this into practice, move the object creation code out of the CACService's parameterless constructor and put it in a factory, instead.
You can then choose to wire up things differently based on things like:
reading in a configuration file
passing in arguments to the factory
creating a different type of factory
Separating types into two categories (types that create things and types that do things) is a powerful technique.
E.g. here's one relatively simple way of doing it using a factory interface -- we simply new up whichever factory is appropriate for our needs and call its Create method. We use a Dependency Injection container (Autofac) to do this stuff at work, but it may be overkill for your needs.
public interface ICACServiceFactory
{
CACService Create();
}
// A factory responsible for creating a 'real' version
public class RemoteCACServiceFactory : ICACServiceFactory
{
public CACService Create()
{
return new CACService(new UserRepository(), new BusinessRepository());
}
}
// Returns a service configuration for local runs & unit testing
public class LocalCACServiceFactory : ICACServiceFactory
{
public CACService Create()
{
return new CACService(
new MemoryUserRepository(),
new MemoryBusinessRepository());
}
}