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How to instantiate outside of a constructor?

How to replicate this code with Autofac syntax?
public static class MenuConfig
{
public static void Initialize()
{
var _menuService = DependecyFactory.GetInstance<IMenuService>();
Parameters.Menu = _menuService.Menu();
}
}
Before calling this a "duplicate question" please note that I'm looking for an Autofac command. I CANNOT inject the interface anywhere and then call "Resolve". What I need to is perform an "InstancePerRequest" inline and uninjected so I don't have to do this:
var _service = new Service(new Dependency(new context()));
LightInject has a method that allows instantiation from an interface OUTSIDE of a constructor like this:
var _service = DependecyFactory.GetInstance<IService>();
What is the equivalent method for Autofac?

When calling containerBuilder.Build() you get back a container which implements IContainer and ILifetimeScope, whenever you get hold of one of these interfaces, you can resolve types from it:
container.Resolve<IService>();
If you want this container to be static, you could add the container as a static property to the Program or Startup class (depending if you're creating a Console or ASP.NET application).
Remember that the root container will be around for the entire duration of your application, so this can result in unwanted memory leaks when used incorrectly. Also see the warning in the documentation.
Still, it's perfectly possible to do the memory management yourself by resolving an Owned<> version from your interface:
using (var service = Program.Container.Resolve<Owned<IService>>())
{
service.Value.UseService();
}
Anyway, since you mention a static class in the comments, the best solution is to change that into a non-static class and register it as a singleton with Autofac. Then you can inject a Func<Owned<IService>> serviceFactory into that singleton and create/dispose an instance of the service wherever you need it.
using (var service = serviceFactory())
{
service.Value.UseService();
}

This is simply not possible with Autofac. All other solutions involving Autofac will require code refactoring which may potentially break software functionality. So unfortunately, the most elegant and least disruptive solution is this:
var _service = new Service(new Dependency(new context()));
Since this is an edge case addressing only one part of the software, this compromise is acceptable. It would be nice, however, if Autofac implemented this functionality in some future release.

Accessing unity container of web app from a class library

I have a class library for caching ( Redis ), we have a unity container inside this Redis class library
public class TCache<T>
{
static readonly IUnityContainer container = new UnityContainer();
private ITCache<T> ICacheStore;
static TCache()
{
container.RegisterType<ITCache<T>, TRedisCacheStore<T>>(new ContainerControlledLifetimeManager());
}
public TCache()
{
ICacheStore = container.Resolve<TRedisCacheStore<T>>();
}
Now my senior said me not use a separate container like this and I should be using the container which is already created inside the web app with the reason being that there should be only one single container.
My question is: is it possible to access a unity container that resides in a different project and is it necessary to do this change ?
Note: I cannot add the reference of the web app into the Redis cache class library.

You should only reference a container within your composition root (http://blog.ploeh.dk/2011/07/28/CompositionRoot/).
In other words, find where your current services are registered, and perform the generic registration there.
Your type that requires a cache store then takes your abstraction via constructor injection:
public class Cache<T>
{
private readonly ITCache<T> cacheStore;
public Cache(ITCache<T> cacheStore)
{
this.cacheStore = cacheStore
?? throw new ArgumentNullException(nameof(cacheStore));
}
}
By the way, using T as a prefix for your types (rather than as a prefix for generic type parameters) is very confusing.
The names TCache and ITCache are also very confusing.

Well, I share his view of the usage of the container. How I fixed this issue is (without going into the details of how I actually created it):
Make an option to register onto the container through an interface. Something like IRegisterContainer.Register(IUnityContainer container).
Then at the moment where you now register the mappings to the container, you extend that function to also search your assembly for all objects that implement that IRegisterContainer and make them register themselves.
And use this as a platform to fix your problem.
If you want to use the IUnityContainer in your TCache object to resolve the TRediscacheStore. Simply let the IUnityContainer register itself.
container.Register<IUnityContainer, container>().
And make it a dependency in the constructor of TCache.

Prism DI container - dispose unnecessary objects

I am facing problem with disposing unnecessary objects from DI container. I use Prism for Xamarin.Forms with Unity container.
Application gets configuration from some database, creates some services using this configuration and registers this services in container using ContainerControlledLifetimeManager. This services are used while resolving views and viewmodels.
When configuration changes application retrieves again changed configuration and now problem comes: how can I remove previous registrations and register new services? If I simply re-register service then previous service is not GC-ed until disposing container.
I cannot dispose container, because it is created and managed by Prism (can I?).
I cannot use child container because Prism will not resolve views and viewmodels using child container (can I?)
Should I use different DI? Does Autofac or other DI support such approach?
EDIT:
I just have tested disposing of re-registered objects in Unity. It came out that re-registering using:
Container.RegisterType<IFoo, Foo>(new ContainerControlledLifetimeManager())
really releases previously registered objects. But I have also registrations using just type:
Container.RegisterType<Foo>(new ContainerControlledLifetimeManager())
or using instance:
Container.RegisterInstance(new Foo())
and these objects are not released when re-registering.
So now the only solution is to reconstruct the Unity container? Or give a try to other ioc container?

Without knowing all of the specifics of what you are looking to accomplish it's impossible to give you a solid roadmap, so I'll touch on some things to consider.
Reregistering Services
If you have some service IFoo, and two implementations FooA and FooB and you initially registered FooA as the implementation for IFoo (with a container controlled lifetime, registering FooB with the container should dispose of the FooA instance and FooB should be generated going forward.
Reconstructing the container
If you have to reconstruct the Container, it should possible. I haven't ever run into a use case where I have had to try something like what you are looking to do. For starters you probably want to take a look at the Initialize method from PrismApplicationBase. This is where the container gets constructed and setup. To handle the reconstruction, you will want to create an event that you subscribe to in your App class.
public partial class App
{
protected override void OnInitialized()
{
var ea = Container.Resolve<IEventAggregator>();
ea.GetEvent<SettingsChangedEvent>().Subscribe(OnSettingsChangedEvent);
// navigate
}
private void OnSettingsChangedEvent()
{
var ea = Container.Resolve<IEventAggregator>();
// prevent a memory leak
ea.GetEvent<SettingsChangedEvent>().Unsubscribe(OnSettingsChangedEvent);
// If you need platform specific types be sure to register either the
// IPlatformInitializer or some similar helper
var platformInitializer = Container.Resolve<IPlatformInitializer>();
ModuleCatalog = CreateModuleCatalog();
ConfigureModuleCatalog();
Container = CreateContainer();
ConfigureContainer();
// This would be your original RegisterTypes, so this assumes you
// look at your settings when initially registering types.
RegisterTypes();
// See notes above
platformInitializer.RegisterTypes(Container);
NavigationService = CreateNavigationService();
InitializeModules();
// Your container is now reset.
var ea = Container.Resolve<IEventAggregator>();
ea.GetEvent<SettingsChangedEvent>().Subscribe(OnSettingsChangedEvent>()
}
}
Containers
As for choosing a container. There is nothing wrong with Unity. Just know that when you're working with Unity, you're going to be stuck with the way it is since it apparently it is a dead project now. Ninject for Prism Forms uses a PCL variant that doesn't seem to be maintained anymore, but when the switch to NetStandard is made Prism will be able to target the current version of Ninject. As for Autofac, there you are dealing with an immutable container so the moment you resolve something you cannot update any new registrations. Autofac for Prism Forms is also a version behind for the same reason as Ninject. DryIoc for Prism forms is a great container and actually the one I am using on all of my current projects. It is also being actively maintained so you can expect use cases you run into to at least be heard.

Thanks for help to Dan S. and R. Richards.
Recreating Prism container caused problems in navigation. Maybe it is possible to fix it but I do not know how.
Using different IOC container would require too much time to learn it.
I ended up with custom lifetime manager (the solution provided in R. Richards link):
class CustomLifetimeManager : LifetimeManager
{
private object _Value;
public override object GetValue()
{
return _Value;
}
public override void RemoveValue()
{
_Value = null;
}
public override void SetValue(object newValue)
{
_Value = newValue;
}
}
Above lifetime manager allows to remove registrations:
public static class UnityContainerExtension
{
/// <summary>
/// Removes registrations that were registred using <see cref="CustomLifetimeManager"/>
/// </summary>
/// <param name="container"></param>
public static void RemoveCustomLifetimeRegistrations(this IUnityContainer container)
{
var registrations = container.Registrations.Where(r => r.LifetimeManagerType == typeof(CustomLifetimeManager));
foreach(var r in registrations)
{
r.LifetimeManager.RemoveValue();
}
}
}

Is it possible to get current Unity container inside controller

I registered unity container like this:
var container = new UnityContainer();
container.RegisterType<ICacheManager, CacheManager>(new ContainerControlledLifetimeManager())
Is it possible to get access to this "container" from controller

Not sure why you need that, but here's the code:
public ActionResult Area51()
{
var _service = DependencyResolver.Current.GetService(typeof (IDummyService));
return View();
}
If what you are trying to do is injecting a Controller, you should set DepedencyResolver to use your IoC container in Global.asax's application start. Then, MVC will inject dependency to your controller automatically.
var container = new UnityContainer();
DependencyResolver.SetResolver(new Unity.Mvc4.UnityDependencyResolver(container));
Look here for more example:
http://www.dotnet-tricks.com/Tutorial/dependencyinjection/632V140413-Dependency-Injection-in-ASP.NET-MVC-4-using-Unity-IoC-Container.html

I'm assuming you're resolving some Controller instance using the container. If that's the case, you can have the controller receive the IUnityContainer as a dependency just like any other.
What are you trying to accomplish? Getting the container in your resolved classes is not great because it couples your classes with the container, and can usually be replaced with other mechanisms.
class Program
{
static void Main(string[] args)
{
var container = new UnityContainer();
var foo = container.Resolve<MyController>();
}
}
public class MyController
{
private IUnityContainer container;
public MyController(IUnityContainer container)
{
this.container = container;
}
}

One way of doing this which I often do for convenience is to declare your container as a global variable in your Global.ascx.cs file like:
public class MvcApplication : System.Web.HttpApplication
{
public static UnityContainer Container;
protected void Application_Start()
{
// assuming your initialize here
}
}
However this is fairly hack-ish.
The correct thing to do would be to use Unity to resolve your Controllers (See this article on creating a unity controller factory), and then allow unity to inject any dependencies into your controller when it resolves the controller.
So a controller like:
public MyController: Controller {
public ICacheManager CacheManager {get;set;}
}
Would automagically resolver any dependencies that your container has registered.

Although it is possible to that, it's best that you avoid it.
It's best that you take any dependencies the controller needs via constructor parameters. This way, the class (controller) makes it clear what are the dependencies required for it to run.
If configured correctly, the container will provide those dependencies and their dependencies (if any), and so on.
The usage of an IoC container should typically be restricted to only one place inside an application (called the composition root). Any extra reference/call to the container is susceptible to lead to the Service Locator anti-pattern. See the linked article for reasons why such an approach may be bad.

how to implement IOC without a global static service (non-service locator solution)?

we want to use Unity for IOC.
All i've seen is the implementation that there is one global static service (let's call it the the IOCService) which holds a reference to the Unity container, which registers all interface/class combinations and every class asks that object: give me an implementation for Ithis or IThat.
Frequently i see a response that this pattern is not good because it leads to a dependency from ALL classes to the IOCService (not to the Unity container because it is only known inside the IOCService).
But what i don't see often, is: what is the alternative way?
Michel
EDIT: found out that the global static service is called the service locator, added that to the title.

The alternative is to have a single instance of your container at the highest application level only, then use that container to resolve every object instance you need to create in that layer.
For example, the main method of most executables just looks like this (minus exception handling):
private static void main(string[] args) {
Container container = new Container();
// Configure the container - by hand or via file
IProgramLogic logic = container.Resolve<IProgramLogic>();
logic.Run();
}
Your program (represented here by the IProgramLogic instance) doesn't have to know anything about your container, because container.Resolve will create all its dependencies - and its dependencies' dependencies, on down to leaf classes with no dependencies of their own.
ASP.NET is a harder case, because web forms doesn't support constructor injection. I typically use Model-View-Presenter in my web forms applications, so my Page classes really only have one dependency each - on their presenter. I don't unit test them (everything interesting and testable is in my presenters, which I do test), and I don't ever substitute presenters. So I don't fight the framework - I just expose a container property on my HttpApplication class (in global.asax.cs) and use it directly from my Page files:
protected void Page_Load(object sender, EventArgs args) {
ICustomerPresenter presenter = Global.Container.Resolve<ICustomerPresenter>();
presenter.Load();
}
That's service locator of course - though the Page classes are the only thing coupled to the locator: your presenter and all of its dependencies are still fully decoupled from your IoC container implementation.
If you have a lot of dependencies in your Page files (that is, if you do not use Model-View-Presenter), or if it's important to you to decouple your Page classes from your Global application class, you should try to find a framework that integrates into the web forms request pipeline and use property injection (as suggested by Nicholas in the comments below) - or write your own IHttpModule and perform the property injection yourself.

+1 for knowing that Service Locator is a Bad Thing.
Problem is - Unity is not very sophisticated so I don't know how easy/hard is it to do IoC the right way with it.
I wrote few blogposts recently that you might find useful.
How I use IoC Containers
Pulling from the container

Instead of using the container explicitly, use it implicitly by leveraging constructor / property injection instead. Create a core class (or set of core classes) that depend on all the major pieces of your application.
Most containers will let you put ISomething[] in your constructor and it will inject all instances of ISomething into your class.
This way, when you bootstrap your application:
Instantiate your container
Register all your goodies
Resolve the core classes (this will pull in all the other dependencies you need)
Run the "main" part of the application
Now, depending on the type of application you are writing, there are different strategies for avoiding marking the IoC container as "static".
For ASP.NET web applications, you'll probably end up storing the container in the Application State. For ASP.NET MVC applications, you need to change out the Controller Factory.
For desktop applications, things get more complicated. Caliburn uses an interesting solution to this problem using the IResult construct (this is for WPF applications but could be adapted for Windows Forms as well.

In theory, to not have to worry about having a static IoC instance, you need to follow the Fight Club Rule - i.e. not to talk about the fight club - i.e. not to mention the IoC container.
This means that your components should largely be unaware about the IoC container. It should only be used at the topmost level when registering components. If a class needs to resolve something, it should really be injected as a dependency.
The trivial case is easy enough. If PaymentService depends on IAccount, the latter should be injected by IoC:
interface IAccount {
Deposit(int amount);
}
interface CreditCardAccount : IAccount {
void Deposit(int amount) {/*implementation*/}
int CheckBalance() {/*implementation*/}
}
class PaymentService {
IAccount account;
public PaymentService (IAccount account) {
this.account = account;
}
public void ProcessPayment() {
account.Deposit(5);
}
}
//Registration looks something like this
container.RegisterType<IAccount, CreditCardAccount>();
container.RegisterType<PaymentService>();
The not so trivial case is where you want to inject multiple registrations. This especialy applies when you are doing any sort of Converntion Over Configuration and creating an object from a name.
For our payment example, say you want to enumerate through all accounts and check their balances:
class PaymentService {
IEnumerable<IAccount> accounts;
public PaymentService (IEnumerable<IAccount> accounts) {
this.accounts = accounts;
}
public void ProcessPayment() {
foreach(var account in accounts) {
account.Chackbalance();
}
}
}
Unity has the ability to register multiple interface to class mappings (they have to have different names thought). It does not, however, automatically inject those into classes that take collections of those registered interfaces. So, the above example will throw a resolution failed exception at runtime.
If you don't care that those objects live forever, you can register PaymentService in a more static fashion:
container.RegisterType<PaymentService>(new InjectionConstructor(container.ResolveAll<IAccount>()));
The above code will register PaymentService and will use a collection of IAccount instances that is resolved at registration time.
Alternatively, you can pass an instance of the container itself as a dependency and let PaymentService perform resolution of accounts. This is not quite following the Fight Club Rule, but is slightly less smelly than static Service Locator.
class PaymentService {
IEnumerable<IAccount> accounts;
public PaymentService (IUnityContainer container) {
this.accounts = container.ResolveAll<IAccount>();
}
public void ProcessPayment() {
foreach(var account in accounts) {
account.Chackbalance();
}
}
}
//Registration is pretty clean in this case
container.RegisterType<IAccount, CreditCardAccount>();
container.RegisterType<PaymentService>();
container.RegisterInstance<IUnityContainer>(container);

If your concern is having a dependency on Unity throughout your application, you can combine the service locator with a facade to hide the IOC implementation. In this way, you do not create a dependency on Unity in your application, only on having something that can resolve types for you.
For example:
public interface IContainer
{
void Register<TAbstraction,TImplementation>();
void RegisterThis<T>(T instance);
T Get<T>();
}
public static class Container
{
static readonly IContainer container;
public static InitializeWith(IContainer containerImplementation)
{
container = containerImplementation;
}
public static void Register<TAbstraction, TImplementation>()
{
container.Register<TAbstraction, TImplementation>();
}
public static void RegisterThis<T>(T instance)
{
container.RegisterThis<T>(instance);
}
public static T Get<T>()
{
return container.Get<T>();
}
}
Now all you need is an IContainer implementation for your IOC container of choice.
public class UnityContainerImplementation : IContainer
{
IUnityContainer container;
public UnityContainerImplementation(IUnityContainer container)
{
this.container = container;
}
public void Register<TAbstraction, TImplementation>()
{
container.Register<TAbstraction, TImplementation>();
}
public void RegisterThis<T>(T instance)
{
container.RegisterInstance<T>(instance);
}
public T Get<T>()
{
return container.Resolve<T>();
}
}
Now you have a service locator that is a facade for IOC services, and can configure your service locator to use Unity or any other IOC container. The rest of the application has no dependency on the IOC implementation.
To configure your service locator:
IUnityContainer unityContainer = new UnityContainer();
UnityContainerImplementation containerImpl = new UnityContainerImplementation(unityContainer);
Container.InitializeWith(containerImpl);
For testing, you can create a stub of IContainer that returns whatever you want, and initialize Container with that.