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Dependency Injection for singelton class with properties

I am having a custom context class in my ASP.NET 4.8 Framework website:
public sealed class MyCustomContext
{
private static readonly Lazy<MyCustomContext> staticContext =
new Lazy<MyCustomContext>(() => new MyCustomContext());
private MyCustomContext()
{
}
public static MyCustomContext Current => staticContext.Value;
public HttpContext Context => HttpContext.Current;
// Logic to return current user based on logged in user
public User LoggedInUser => ...
// Logic to return SiteWideSettings
public Collection<SiteWideSettings> SiteWideSettings => ...
}
The above class is a Singleton and the usage of the above class in my service class methods is like this:
public class MyService : IMyService
{
public MyService()
{
}
public void DoWork()
{
var current = MyCustomContext.Current;
var loggedInUser = current.LoggedInUser;
var siteWideSettings = current.SiteWideSettings;
var currentContext = current.Context;
// use the above properties further for this method
}
}
My goal is to remove MyCustomContext class dependency hardcoded in my DoWork method of MyService class so that it can look like this:
public class MyService : IMyService
{
private readonly IMyCustomContext _myCustomContext;
public MyService(IMyCustomContext myCustomContext)
{
_myCustomContext = myCustomContext;
}
public void DoWork()
{
var current = _myCustomContext.Current;
var loggedInUser = current.LoggedInUser;
var siteWideSettings = current.SiteWideSettings;
var currentContext = current.Context;
// use the above properties further for this method
}
}
Can you share how to convert my MyCustomContext class so that it can be injected via dependency injection into MyService?
I have one more question, do the properties like LoggedInUser, SiteWideSettings and Context of MyCustomContext class should be written as properties or they should be converted to methods for dependency injection?

For the dependency injection you need an interface which gets initialized, so your MyCustomContext class needs to implement a new interface called IMyCustomContext. The interface can look like following:
public interface IMyCustomContext
{
HttpContext Context { get; }
User LoggedInUser { get; }
Collection<SiteWideSettings> SiteWideSettings { get; }
}
public class MyCustomContext : IMyCustomContext
{
public HttpContext Context
{
get { return HttpContext.Current; }
}
public User LoggedInUser
{
get
{
// Logic to return current user based on logged in user
}
}
public Collection<SiteWideSettings> SiteWideSettings
{
get
{
// Logic to return SiteWideSettings
}
}
}
In the Startup.cs there is a method called ConfigureServices, there you can add the following for the dependency injection:
container.RegisterType<IMyCustomContext, MyCustomContext>(
TypeLifetime.Singleton);

It's worth pointing out that Singleton has dual meaning here:
The Singleton Design Pattern ensures an object is only instantiated once. Its implementation isn't ideal though, as it relies on ambient state.
The Singleton Lifetime is used by IOC frameworks, where it ensures the same reference of an object is used every time.
In short, the Singleton Lifetime effectively removes the need to implement the Design Pattern, because the IOC framework ensures the backing concept for you.
Meaning, if we register our dependency with the Singleton Lifetime.
container.RegisterType<ICustomContext, MyCustomContext>(TypeLifetime.Singleton);
We can remove the code for the Singleton Pattern, as the IOC container will take over the responsibility of guarding the single instance/reference.
public class MyCustomContext : ICustomContext
{
public HttpContext Context => HttpContext.Current;
// Logic to return current user based on logged in user
public User LoggedInUser => ...
// Logic to return SiteWideSettings
public Collection<SiteWideSettings> SiteWideSettings => ...
}
I've also added the ICustomContext interface with the member we're interested in.
public interface ICustomContext
{
HttpContext Context { get; }
User LoggedInUser { get; }
Collection<SiteWideSettings> SiteWideSettings { get; }
}
Can you share how to moq properties of that class?
That's right, we just moved the problem one level, didn't we? If you need to extract an interface, you usually need to do this in a recursive manner.
This also means HttpContext is not a good candidate for an interface member, which makes sense when you think about it. From a unit test's point of view, we're not interested in verifying ASP.NET's inner workings. Instead, we want to check our own code, and only that portion, with no dependencies on foreign libraries. To do so, you should only copy the HttpContext members you need on to your interface and remove the dependency on HttpContext (which is notoriously hard to abstract).
For example:
public interface ICustomContext
{
IPrincipal User { get; }
User LoggedInUser { get; }
Collection<SiteWideSettings> SiteWideSettings { get; }
}
This will require some refactoring / remodeling as the number of properties grows.
For simple DTO's you can even choose not to abstract / interface them, as long as your able to easily create fakes for unit testing. Also remember it only makes sense to introduce an interface if there are going to be multiple implementations.
One more thing about Dependency Inversion, and how IOC frameworks work, you usually let the dependencies bubble up. The recommended approach is through constructor injection, as illustrated in the following ICustomContext implementation for unit tests.
public class TestCustomContext : ICustomContext
{
public MyCustomContext(IPrincipal user, User loggedInUser, Collection<SiteWideSettings> siteWideSettings)
{
User = user;
LoggedInUser = loggedInUser;
SiteWideSettings = siteWideSettings;
}
IPrincipal User { get; }
User LoggedInUser { get; }
Collection<SiteWideSettings> SiteWideSettings { get; }
}
I have one more question, do the properties like LoggedInUser, SiteWideSettings and Context of MyCustomContext class should be written as properties or they should be converted to methods for dependency injection?
You can have both. If the state was injected through constructor injection, you might as well expose it as a property. If the implementing class implements behavior to create / transform the state, you might want to expose the behavior as a method. It all depends on the actual case, there is no golden bullet here. Just remember that in OO design, interfaces are used to model behaviors, with their scope kept as small as possible.
UPDATE
Those properties are not getting filled via constructor. All of these properties "IPrincipal User { get; } User LoggedInUser { get; } Collection SiteWideSettings { get; }" have the body in their getter, they get the data from cache first and if not found then it calls the service to get the data from db for those properties (all that is written in in the get of those properties). Should I keep them as properties only or make them methods?
Let me split up your question.
Should I keep them as properties only or make them methods?
From a technical point of view, it doesn't really matter. Properties, or automated properties (like the ones you're using), are just syntactic sugar over full blown methods. Meaning, they all get compiled into equivalent CIL instructions.
That leaves only the human factor. The readability and maintainability of your code. The agreed upon coding style and practices. That's not something I can answer for you. Personally, I prefer methods for handling these kind of code flows.
they get the data from cache first and if not found then it calls the service to get the data from db for those properties (all that is written in in the get of those properties).
Sounds like this class is more of a service provider than an actual model class in your domain. As there's also I/O involved, I'd definitely recommend switching to asynchronous methods on your interface. The explicit (Task based) signature says a lot to fellow developers reading your code.
The part where I talked about the dependencies bubbling up plays an important role here. The cache and repository are both dependencies of MyCustomContext. IOC and its inherent Dependency Inversion Principle rely on the explicit declaration of dependencies, as shown in the following sample. Note the implementation of GetLoggedInUser() is not what matters here, rather the way the dependencies are set through the constructor. All these dependencies need to be registered with your IOC container first, for it to be able to resolve ICustomContext.
public class MyCustomContext : ICustomContext
{
private readonly IUsersCache _usersCache;
private readonly IUsersRepo _usersRepo;
public MyCustomContext(IUsersCache usersCache, IUsersRepo usersRepo, IPrincipal principal)
{
_usersCache = usersCache;
_usersRepo = usersRepo;
Principal = principal;
}
public IPrincipal Principal { get; }
public async Task<LoggedInUser> GetLoggedInUser()
{
var userId = await GetUserId(Principal);
var user = _usersCache.GetById(userId);
if (user == null)
{
user = _usersRepo.GetById(userId);
_usersCache.Add(user);
}
return user;
}
...
}
Those properties are not getting filled via constructor. All of these properties "IPrincipal User { get; } User LoggedInUser { get; } Collection SiteWideSettings { get; }" have the body in their getter
I don't think that's true for IPrincipal as it, together with HttpContext, is instantiated by ASP.NET behind the scenes. All you need to do is tell the IOC container how to resolve the current IPrincipal and let it work its magic.
Likewise, all classes that depend on ICustomContext should have it injected by the IOC container.
public class MyService : IMyService
{
private readonly ICustomContext _customContext;
public MyService(ICustomContext customContext)
{
_customContext = customContext;
}
public async Task DoWork()
{
var currentPrincipal = _customContext.Principal;
var loggedInUser = await _customContext.GetLoggedInUser();
...
}
}
An important part here is again unit testing. If you design your classes like this, you can easily create fakes for testing. And even if there wasn't any testing involved, which I wouldn't recommend, the ability to decouple classes like this is a good indication of a well designed code base.

Single Responsibility Principle Concerns (Am I thinking about refactoring properly)

My current class PropertyManager looks like this:
public class PropertyManager : IDisposable
{
private readonly IPropertyRepo _propertyRepo;
private readonly IUserTypeRepo _userTypeRepo;
public PropertyManager(IPropertyRepo propertyRepo, IUserTypeRepo userTypeRepo = null)
{
if (propertyRepo == null)
throw new ArgumentNullException("propertyRepo");
_propertyRepo = propertyRepo;
if (userTypeRepo != null)
_userTypeRepo = userTypeRepo;
}
}
My Property Manager will use the _userTypeRepo in some method to accomplish some task. I think I want to implment a rule that says "Each Manager(Service,Factory,etc) should be responsible for its own repository."
The idea:
The PropertyManager, because it needs to do something with the UserTypeRepo, I should be using the UserManager for such activities.
As such, this means that I will not provide a repo when creating an instance of the UserManager (i.e., var usrMgr = new UserManager(); // no repo). Instead, the UserManager will use the default constructor which will create a new instance of the IUserTypeRepo and provide a new instance of a UserManager and then it can do its work.
I think this accomplishes some design principle such as Separation of Concerns and the Single Responsibility, but then I may be getting away from my Dependency Injection design pattern as the new Managers would now have multiple constructors and look like this:
public class PropertyManager : IDisposable
{
private readonly IPropertyRepo _propertyRepo;
public PropertyManager(){
// use the default repo
_propertyRepo = new PropertyRepo();
}
// Used from Controller or Unit Testing
public PropertyManager(IPropertyRepo propertyRepo)
{
if (propertyRepo == null)
throw new ArgumentNullException("propertyRepo");
}
}
public class UserManager : IDisposable
{
private readonly IUserRepo _userRepo;
public UserManager(){
// use the default repo
_userRepo = new UserRepo();
}
// Used from Controller or Unit Testing
public UserManager(IUserRepo userRepo)
{
if (userRepo == null)
throw new ArgumentNullException("userRepo");
}
}
Would this be frowned upon? Or am I on the right track? In either case, why and thanks?
Update. After reading Yawar's post I decided to update my post and I think I have a relevant concern.
Let's think of a real world example of the above. I have a PropertyManager in real life named "Robert" one of the jobs he performs each morning at work is to Open() the Property (i.e., he unlocks the Property he is the Manager of). I also have a UserManger who manages people who visit the Property and her name is "Sarah" she has a function that she does called EnterProperty() (which is what she does in the morning when she physically walks into the building).
Rule: UserManager has a dependency on PropertyManager when using the EnterProperty()
This looks like this according to all accepted standards:
Property Manager
class PropertyManager : IPropertyManager
{
private readonly IPropertyRepo _propertyRepo;
public PropertyManager(IPropertyRepo propertyRepo)
{
if (propertyRepo == null)
throw new ArgumentNullException("propertyRepo");
this._propertyRepo = propertyRepo;
}
// this is when Robert opens the property in the morning
public void Open()
{
_propertyRepo.Open();
}
// this is when Robert closes the property in the evening
public void Close()
{
_propertyRepo.Close();
}
// this answers the question
public bool IsOpen()
{
return _propertyRepo.IsOpen();
}
}
User Manager
class UserManager : IUserManager
{
private readonly IPropertyRepo _propertyRepo;
private readonly IUserRepo _userRepo;
public UserManager(IUserRepo userRepo, IPropertyRepo propertyRepo = null)
{
if (userRepo == null)
throw new ArgumentNullException("userRepo");
this._userRepo = userRepo;
if (propertyRepo != null)
this._propertyRepo = propertyRepo;
}
// this allows Sarah to physically enter the building
public void EnterProperty()
{
if(_propertyRepo.IsOpen())
{
Console.WriteLine("I'm in the building.");
}else{
_propertyRepo.Open(); // here is my issue (explain below)
Console.WriteLine("Even though I had to execute the Open() operation, I'm in the building. Hmm...");
}
}
}
Web API Controller
{
public void OpenForBusiness(){
private const IPropertyRepo propertyRepo = new PropertyRepo();
private IPropertyManager propertyManager = new PropertyManager(propertyRepo);
private IUserManager userManager = new UserManager(new UserRepo(), propertyRepo);
// Robert, the `PropertyManager`, opens the `Property` in the morning
propertyManager.Open();
// Sarah, the `UserManager`, goes into `Property` after it is opened
userManager.EnterProperty();
}
}
Now, everything is cool and I can walk away and I now have a Repository Pattern which use Dependency Injection which supports TDD and not tightly coupled classes among other benefits.
However, is the truly realistic? (explain why I ask in second)
I think a more real-world (realistic) approach is one that does:
Web API Controller
public void Method1()
{
private IPropertyManager propMgr = new PropertyManager(new PropertyRepo());
private IUserManager userMgr = new UserManager(new UserRepo()); // no dependencies on any repository but my own
// 1. Robert, the `PropertyManager`, opens the `Property`
propMgr.Open();
// 2. Check to see if `Property` is open before entering
// choice a. try to open the door of the `Property`
// choice b. call or text Robert, the `PropertyManager`, and ask him if he opened the `Property` yet, so...
if(propMgr.IsOpen()){
// 3. Sarah, the `UserManager`, arrives at work and enters the `Property`
userMgr.EnterProperty();
}else{
// sol, that sucks, I can't enter the `Property` until the authorized person - Robert - the `PropertyManager` opens it
// right???
}
}
the EnterProperty() method on the UserManager now looks like this:
// this allows Sarah to physically enter the building
public void EnterProperty()
{
Console.WriteLine("I'm in the building.");
}
The promised explanation from above:
If we think in real-world terms we must agree that the later is preferred over the former. When thinking of a Repository lets say this is the definition of ones self (i.e., one's Person) (i.e., the UserRepo having all the data related to the User, is to the UserManager as the DNA, Heartbeat, Brain Wave Pattern, etc. is to a Human (the HumanRepo). As such, allowing the UserManager to know about the PropertyRepo and having access to its Open() method violates all Real-World security principles and Business Rules. In reality this says that through My Contructor() I can get an Interface Representation of a PropertyRepo that I can use any way I see fit. This is synonymous to the following logic of the HumanRepo:
I, Sarah - a UserManager - through a new instance of myself with the satisfaction of the PropertyRepo through my Constructor() create a Hologram Interface of Robert, the PropertyManager that I can use any way I see fit. Granted right now I only want to use the IsOpen() method of the PropertyRepo I actually use the Open() method to do it myself if Robert has not yet performed his duty. This is a security concern to me. In the real-world this says I don't have to wait for Robert to open the Property and use the Holocopy of him and implement his Open() method to get access.
That doesn't seem right.
I think with the last implementation I get SoC, SRP, DI, Repository Pattern, TDD, and Logical Security and as close to a real-world implementation as possible.
What do you all think?

I think I agree with your SoC and breaking the PropertyManager class into PropertyManager and UserManager classes. You are almost there.
I would just refactor as shown below:
public class PropertyManager : IDisposable, IPropertyManager
{
private readonly IPropertyRepo _propertyRepo;
// Used from Controller or Unit Testing
public PropertyManager(IPropertyRepo propertyRepo)
{
if (propertyRepo == null)
throw new ArgumentNullException("propertyRepo");
this._propertyRepo = propertyRepo;
}
}
public class UserManager : IDisposable, IUserManager
{
private readonly IUserRepo _userRepo;
// Used from Controller or Unit Testing
public UserManager(IUserRepo userRepo)
{
if (userRepo == null)
throw new ArgumentNullException("userRepo");
this._userRepo = userRepo;
}
}
Note: Just extract IPropertyManager & IUserManager so that the calling classes will depend upon the interfaces and provide the implementation.
Creating parameterless constructor is useless if you want to (you should) force the client to provide the concrete implementation of IPropertyRepo and IUserRepo interfaces.
public PropertyManager(){
// use the default repo
_propertyRepo = new PropertyRepo();
}
I dont think you would need
if (propertyRepo == null)
throw new ArgumentNullException("propertyRepo");
or
if (userRepo == null)
throw new ArgumentNullException("userRepo");
as IPropertyRepo and IUserRepo will be resolved via a IoC at the startup of your application (say its MVC then before calling the controller IoC will resolve them) so no need to check for null. I have never checked the dependencies for null in my code.
From what you have posted here thats pretty much it.
Unit of Work pattern is used for repository layer not in the manager layer. I would delete that from the title.
Hope this helps!

I think this accomplishes some OOP goal such as Separating Concerns
and the Single Responsibility Principle.
The result is opposite. Now, PropertyManager tightly couples to PropertyRepo; previously, they were loosely coupled.
First approach is better than the latter one. However, PropertyManager and UserManager should not create other objects on which they rely to do their work. The responsibility for creating and managing object should be offloaded to IoC container.
Interfaces describe what can be done, whereas classes describe how it is done. Only classes involve the implementation details—interfaces are completely unaware of how something is accomplished. Because only classes have constructors, it follows that constructors are an implementation detail. An
interesting corollary to this is that, aside from a few exceptions, you can consider an appearance of the new keyword to be a code smell. - Gary McLean Hall
Answer for Updated Question:
In your updated question, you combine Service/Manager and somewhat Domain into a single class - PropertyManager, UserManager. It becomes personal preference.
I personally like to keep them separate. In addition, I like to use Role based and Claim based authorization. Let me use my GitHub sample project as a reference. Please feel free to clone it.
User Domain
User class is also used by Entity Framework Code First Fluent API.
public partial class User
{
public int Id { get; set; }
public string UserName { get; set; }
public string FirstName { get; set; }
}
User Service
public class UserService : IUserService
{
private readonly IRepository<User> _repository;
public UserService(IRepository<User> repository)
{
_repository = repository;
}
public async Task<IPagedList<User>> GetUsersAsync(UserPagedDataRequest request)
{
...
}
}
Action Method
Notice that UI related Business Logic stays at UI layer.
public async Task<ActionResult> Login(LoginModel model, string returnUrl)
{
if (ModelState.IsValid)
{
bool result = _activeDirectoryService.ValidateCredentials(
model.Domain, model.UserName, model.Password);
if (result)
{
...
}
}
...
}

you can take quite a bit of a different approach.....( ignoring your repositories, but allowing for it to be injected )
In this system, the property is only readable, with an event system to handle the mutations, the event system also has rules system which controls what mutations are allowed. This means even if you have a property object you can't mutate it without going through its rules.
This code is more conceptual. The next logical step is to use a full actor model and something like (akka.net) and you may find your repository pattern just disappearing :)
public class Property
{
public string Name { get; private set; }
private IPropertyRules _rules;
private List<User> _occupants = new List<User>();
private IEventLog _eventLog;
public Property(IPropertyRules rules, IEventLog eventLog)
{
_rules = rules;
_eventLog = eventLog;
}
public ActionResult Do(IAction action, User user)
{
_eventLog.Add(action, user);
if (_rules.UserAllowedTo(action, user, this))
{
switch (action)
{
case Open o:
Open();
return new ActionResult(true, $"{user} opened {Name}");
case Enter e:
Enter(user);
return new ActionResult(true, $"{user} entered {Name}");
}
return new ActionResult(false, $"{Name} does not know how to {action} for {user}");
}
return new ActionResult(false, $"{user} is not allowed to {action} {Name}");
}
private void Enter(User user)
{
_occupants.Add(user);
}
private void Open()
{
IsOpen = true;
}
public bool IsOpen { get; set; }
}
public interface IEventLog
{
void Add(IAction action, User user);
}
public class Enter : IAction
{
}
public interface IPropertyRules
{
bool UserAllowedTo(IAction action, User user, Property property);
}
public class Open : IAction
{
}
public class ActionResult
{
public ActionResult(bool successful, string why)
{
Successful = successful;
WhatHappened = why;
}
public bool Successful { get; private set; }
public string WhatHappened { get; private set; }
}
public interface IAction
{
}
public class User
{
}

Injecting dependencies into AuthorizeAttribute in a class library

I've run into an interesting design issue with a class library I am writing. I have a custom implementation of the AuthorizeAttribute that I want clients to be able to use like this:
[Protected("permission_name")]
In the above code, PermissionAttribute inherits from AuthorizeAttribute and uses a local default (DefaultContext created using HttpContext).
Behind the scenes, the attribute uses a SecurityService to check users, roles and permissions against (the SecurityService itself uses a client-provided persistence service that they can wire up in the composition root of their app).
So my attributes need a reference to the SecurityService to function. Since Attribute constructors can only have compile-time constants, I cannot use constructor injection.
I don't want to force my clients to use a DI framework - they should be able to discover and wire up the necessary dependencies in their composition root without using an IoC library, if they so choose.
Here are my options:
Have the library use a singleton SecurityService.
Use property injection, which would work but
it would make the dependency seem optional, which it is not and
I don't know where I can do property injection in an MVC app on an authorize attribute.
A possible solution to 2. above is to do set an instance of SecurityService as a static property on the attribute at application startup and use a guard clause to prevent it from being set more than once, like this:
class ProtectedAttribute : ...
{
private static ISecurityService _SecurityService ;
public static ISecurityService SecurityService
{
get
{
return _SecurityService ;
}
set
{
if (_SecurityService != null)
throw new InvalidOperationException("You can only set the SecurityService once per lifetime of this app.") ;
_SecurityService = value ;
}
}
}
The SecurityService could be an abstract service facade so that it can be extended/replaced by a different implementation.
Is there a better way to solve this problem?
UPDATE: Adding some code to show how I am going to do it:
Add a public property on the attribute that returns the permission name:
public class ProtectedAttribute : ...
{
private string _Permission ;
public string Permission { get { return _Permission ; } /*...*/ }
public ProtectedAttribute(string permission) { /*...*/ }
}
Setup an authorization filter and configure dependency via Ninject (if using Ninject):
using Ninject.Web.Mvc.FilterBindingSyntax;
public class MyModule : Ninject.Modules.NinjectModule
{
public override void Load()
{
// mySecurityService instance below can have a singleton lifetime - perfect!
this.BindFilter<MyAuthorizationFilter>(FilterScope.Action, 0)
.WhenActionMethodHas<ProtectedAttribute>()
.WithConstructorArgument("securityService", mySecurityService)
.WithConstructorArgumentFromActionAttribute<ProtectedAttribute>("permission", p => p.PermissionName) ;
}
}
Ohhh it's...beautiful sniffle

With ASP.NET MVC 3 you could use constructor injection with action filters thanks to the new IFilterProvider. This way you no longer need to decorate your controller actions with action filters. You could apply them thanks to this interface and using a marker attribute.
And if you don't wanna bother implementing it manually you could always use an existing DI framework such as Ninject which provides a fluent way to define action filter dependencies.

My applications inherit from a base Application class that exposes the IOC container.
public interface IInjectableApplication
{
IUnityContainer Container { get; }
}
Then I have a base attribute class, which is aware of this
public abstract IocAwareActionFilterAttribute : ActionFilterAttribute{
protected T ResolveItem<T>(ResultExecutedContext context)
{
var app = context.HttpContext.ApplicationInstance as IInjectableApplication;
if (app == null) { throw new NullReferenceException("Application is not IInjectable."); }
T c = (T)app.Container.Resolve(typeof(T));
if (c == null) { throw new NullReferenceException(string.Format("Could not find injected {0}.", typeof(T).FullName)); }
return c;
}
}
While this is not true Injection, since Attributes aren't constructed 'normally', this provides a similar behavior. No reason it should not be adaptable to other IOCs

Best practice to access an HttpContext session outside the controller in a separate helper class

Is it a good practice to access a HttpContext session outside the controller in separate helper class?
====================
Should the controller take all the responsibility of getting the data from the session and transfer to a helper class
Example
HomeController : BaseController
{
var value1 = Httpcontext.Session["key1"];
var value2 = Httpcontext.Session["key2"];
var val...
CallAMethod(value1,value2,val...);
}
Or should it mock HttpContextBase and use it as in the following?
HomeController : BaseController
{
//Use Dependency Injection pattern
CallAMethod(base.SessionWrapper);
}
Implementation of ISessionWrapper is
public interface ISessionWrapper
{
T GetFromSession<T>(string key);
SetInSession(string key, object value);
}
public class HttpContextSessionWrapper : ISessionWrapper
{
private T GetFromSession<T>(string key)
{
return (T) HttpContext.Session[key];
}
private void SetInSession(string key, object value)
{
HttpContext.Session[key] = value;
}
}
public class BaseController : Controller
{
public ISessionWrapper SessionWrapper { get; set; }
public BaseController()
{
SessionWrapper = new HttpContextSessionWrapper();
}
}

Apparently you want to have some testability in your code (after all that's why you're going through the burden of creating an ISessionWrapper).
Both approaches have ups and downs.
Using the HttpContext directly
Quicker to develop
Need some thoughts on testing class. Nemely the ability to emulate a HttpContext. Doable with library available on the NET.
Using dependency injection (ISessionWrapper):
Slower to develop
Need to "reinvent the wheel" regarding access to the HttpContext
A lot more code to write and mantain
So, I would ponder the pros and cons of both approaches and decide depending on my goals.
However, personally, I would choose the path that require a lot less code to write.
Edited to Add
In reply to the heart of the question (after a nag in from the OP) the controller should always manage the data gathering before passing them to the actuators.

AOP: Custom Model Binder Attribute using Ninject

In short: I am trying to create a custom model binder that will take in the type of user and get their id, then use a service class to retrieve the strongly typed object.
If there is a better way to do this, please let me know.
Elabaration:
I have ninject setup with all my bindings within my DomainService layer, 3 web ui's are hooked up to the domain service layer. Each asp.net mvc app loads the bindings into the kernal.
//my custom model binder
public class UserModelBinder : IModelBinder
{
private IAuthenticationService auth;
public UserModelBinder(IAuthenticationService _auth, EntityName type,
string loggedonuserid)
{
this.auth = _auth;
CurrentUserType = type;
CurrentUserId = loggedonuserid;
}
public EntityName CurrentUserType { get; private set; }
private string CurrentUserId { get; set; }
public object BindModel(ControllerContext controllerContext,
ModelBindingContext bindingContext)
{
object loggedonuser = null;
if (CurrentUserType == EntityName.Client)
loggedonuser = GetLoggedOnClientUser(CurrentUserId);
else if (CurrentUserType == EntityName.Shop)
loggedonuser = GetLoggedOnShopUser(CurrentUserId);
else
throw new NotImplementedException();
return loggedonuser;
}
public ClientUser GetLoggedOnClientUser(string loggedonuserid)
{
var user = _auth.GetLoggedOnClientUser(loggedonuserid);
if (user == null)
throw new NoAccessException();
return user;
}
public ShopUser GetLoggedOnShopUser(string loggedonuserid)
{
var user = _auth.GetLoggedOnShopUser(loggedonuserid);
if (user == null)
throw new NoAccessException();
return user;
}
}
my Global.aspx.cs
// using NInject to override application started
protected override void OnApplicationStarted()
{
AreaRegistration.RegisterAllAreas();
// hand over control to NInject to register all controllers
RegisterRoutes(RouteTable.Routes);
//how do I instantiate?
ModelBinders.Binders.Add(typeof(object), new
UserModelBinder(null,EntityName.Client, User.Identity.Name));
}
My problem is IAuthentication is a service, it is connected to other things like a repository, how do I actually instantiate this properly? Should I create a new NinjectModule? I am really confused with this so any help is greatly appreciated. I have tried to pass in Container.Get(); - but it is null...
NOTE: the reason why I am creating a modelbinder- all controllers will require the type of user as I my service layer requires which type of user is making a request, most methods in my service layer will have overloads where it will do one thing for a ShopUser or ClientUser or any other user in the system...
EDIT:
I could very easiy within my controller call upon the IAuthenticationService and get the type of user and pass into my domainservice layer to process the relevant tasks but I just want to know how it is possible with the ModelBindings (and if it makes sense to do it that way).
Edit2: Is there a working sample of using a custom Attribute with AOP with the custom attribute calling/binding/getting an instance of ISomethingService?

You can use the Service Locator pattern here. Pass the Ninject Container (IKernel?) to the constructor and resolve the AuthenticationService each time you need to bind something.
A refinement of this could be to have a constructor argument Func where you pass the function to resolve the service. This would be more explicit and removes the dependency on Ninject. Something like this:
public class MyModelBinder : IModelBinder
{
Func<IAuthenticationService> _resolveAuthService;
public MyModelBinder(Func<IAuthenticationService> resolveAuthService)
{
_resolveAuthService = resolveAuthService;
}
public override object Bind(Context c)
{
var authService = _resolveAuthService();
authService.GetSomething();
// etc...
}
}