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Microsoft.Extensions.Options Do you have to keep passing it through the full stack manually

I'm implementing appsettings.json in place of app.config for the first time so please excuse the potentially stupid question to which I have not been able to find a satisfactory solution in my research.
I have a solution fronted by a .Net Core 2.0 Web API with dependent projects breaking my solution up into layers of class libraries. I need to get to the connection string stored in my top layer appsettings.json (under my Web API) from the bottom persistence layer class library.
I found this article explaining it step by step. and finally got it to work.
Note: I tested this functionality with the connectionString but I need other variables as well which I was planning to do later.
My question is that once I implemented the required constructor:
public Data(IOptions<ConnectionStrings> connectionStrings)
{
ConnectionStrings = connectionStrings;
}
I have to manually pass the IOptions object all the way through the stack.
Data date = new Data(ConnectionStrings);
Is there no solution similar to what ConfigurationManager gave you that does not require me to pass the IOptions object all the way through?
Surely I'm doing something wrong, no?

I had a similar concern when I was building my first dotnet core 2 application. The solution I came up with was to configure dependency injection to resolve T as IOptions<T>.Value, for example:
services.AddTransient<SomeOptions>(sp =>
sp.GetService<IOptions<SomeOptions>>().Value);
This works well if you are using dependency injection for objects that require SomeOptions to be supplied in the constructor. Doesn't really provide much value if you are manually "newing" up objects.
I'm not entirely sure what your application looks like, but from your example above you have a Data class which takes an IOptions<ConnectionStrings> parameter in the constructor.
Given the following code in your startup:
// I don't have your entire project - just looking at your link above, I came up with this
services.Configure<ConnectionStrings>
(Configuration.GetSection("ConnectionStrings"));
services.AddTransient<ConnectionStrings>(sp =>
sp.GetService<IOptions<ConnectionStrings>>().Value);
services.AddTransient<Data>();
You could have your Data class defined as such:
public class Data
{
private readonly ConnectionStrings _connectionStrings;
public Data(ConnectionStrings connectionStrings)
{
//I don't know what you need to do with this here - just guessing
_connectionStrings = connectionStrings;
}
}
You could have your controller class defined as such:
public class SomeController
{
private readonly Data _data;
public SomeController(Data data)
{
_data = data;
}
public IActionResult Get()
{
// do something with _data here
// don't new it up - it gets injected!
}
...
}

StructureMap and HTTP request-scoped services - why is my service created twice in a single scope?

I have an ASP.NET MVC application using StructureMap.
I have created a service called SecurityContext which has a static Current property. A simplified version looks like this:
public class SecurityContext : ISecurityContext
{
public bool MyProperty { get; private set; }
public static SecurityContext Current
{
get
{
return new SecurityContext() { MyProperty = true };
}
}
}
I've hooked this up in my StructureMap registry as follows:
For<ISecurityContext>().Use(() => SecurityContext.Current);
My understanding of this Linq expression overload of the Use method is that the returned concrete object is the same for the entire HTTP request scope.
However, I've set up a test case where my context interface is injected in two places, once in the controller's constructor and again using the SetterProperty attribute in the base class my view inherits from.
When debugging I observe the Current static method being hit twice so clearly my assumptions are wrong. Can anyone correct what I'm doing here? The reason I want this request-scoped is because I'm loading certain data into my context class from the database so I don't want this to happen multiple times for a given page load.
Thanks in advance.

The default lifecycle for a configuration is Transient, thus each request for an ISecurityContext will create a new instance of SecurityContext. What I think you want is to use the legacy HttpContext lifecycle.
Include the StructureMap.Web nuget package. Then change your configuration to the following:
For<ISecurityContext>()
.Use(() => SecurityContext.Current)
.LifeCycleIs<HttpContextLifecycle>();
More information on lifecyles can be found here.
The HttpContextLifecycle is obsolete, however I do not know if or when it will be removed. The StructureMap team does recommend against using this older ASP.Net lifecycle. They state in the documentation that most modern web frameworks use a nested container per request to accomplish the same scoping. Information about nested containers can be found here.
I don't know if the version of ASP.Net MVC you are using is considered a modern web framework. I doubt it is because ASP.Net Core 1.0 is the really the first in the ASP.Net line to fully embrace the use of DI. However, I will defer to #jeremydmiller on this one.

Injecting runtime value into Unity dependency resolver

I am working on a webapi project and using Unity as our IOC container. I have a set of layered dependencies something like the following:
unityContainer.RegisterType<BaseProvider, CaseProvider>(new HierarchicalLifetimeManager());
unityContainer.RegisterType<IRulesEngine, RulesEngine>();
unityContainer.RegisterType<IQuestionController, QuestionController>();
unityContainer.RegisterType<IAPIThing, WebAPIThing>();
Now the constructor for BaseProvider accepts an int as a parameter which is the Case identifier. WebAPIThing takes a BaseProvider in its constructor. Normally in a non web scenario I would inject the case id using something like:
public static IAPIThing GetIAPIThing(int caseId)
{
return CreateUnityContainer().Resolve<IAPIThing >(new ParameterOverride("caseId", caseId).OnType<CaseProvider>());
}
But that only works when I explicitly call that method. In a Web API scenario I am using a
config.DependencyResolver = new UnityDependencyResolver(unityContainer); to resolve my api controllers.
I would guess I will still need to influence how the DependencyResolver resolves that BaseProvider object at runtime.
Anyone had to do something similar?
EDIT 1
I have tried using the following which appears to work:
unityContainer.RegisterType<BaseProvider>(
new HierarchicalLifetimeManager()
, new InjectionFactory(x =>
new CaseProvider(SessionManager.GetCaseID())));

You are trying to inject a runtime value (the case id) into the object graph, which means you are complicating configuration, building, and verification of the object graph.
What you should do is promote that primitive value to its own abstraction. This might sound silly at first, but such abstraction will do a much better job in describing its functionality. In your case for instance, the abstraction should probably be named ICaseContext:
public interface ICaseContext
{
int CurrentCaseId { get; }
}
By hiding the int behind this abstraction we effectively:
Made the role of this int very explicit.
Removed any redundancy with any other values of type int that your application might need.
Delayed the resolving of this int till after the object graph has been built.
You can define this ICaseContext in a core layer of your application and everybody can depend on it. In your Web API project you can define a Web API-specific implementation of this ICaseContext abstraction. For instance:
public class WebApiCaseContext : ICaseContext
{
public int CurrentCaseId
{
get { return (int)HttpContext.Current.Session["CaseId"];
}
}
This implementation can be registered as follows:
unityContainer.RegisterType<ICaseContext, WebApiCaseContext>();
UPDATE
Do note that your own new CaseProvider(SessionManager.GetCaseID()) configuration does not solve all problems, because this means that there must be a session available when verifying the object graph, which will neither be the case during application startup and inside a unit/integration test.

SimpleInjector - Register Object that depends on values from another registered object

Using SimpleInjector, I am trying to register an entity that depends on values retrieved from another registered entity. For example:
Settings - Reads settings values that indicate the type of SomeOtherService the app needs.
SomeOtherService - Relies on a value from Settings to be instantiated (and therefore registered).
Some DI containers allow registering an object after resolution of another object. So you could do something like the pseudo code below:
container.Register<ISettings, Settings>();
var settings = container.Resolve<ISettings>();
System.Type theTypeWeWantToRegister = Type.GetType(settings.GetTheISomeOtherServiceType());
container.Register(ISomeOtherService, theTypeWeWantToRegister);
SimpleInjector does not allow registration after resolution. Is there some mechanism in SimpleInjector that allows the same architecture?

A simple way to get this requirement is to register all of the available types that may be required and have the configuration ensure that the container returns the correct type at run time ... it's not so easy to explain in English so let me demonstrate.
You can have multiple implementations of an interface but at runtime you want one of them, and the one you want is governed by a setting in a text file - a string. Here are the test classes.
public interface IOneOfMany { }
public class OneOfMany1 : IOneOfMany { }
public class OneOfMany2 : IOneOfMany { }
public class GoodSettings : ISettings
{
public string IWantThisOnePlease
{
get { return "OneOfMany2"; }
}
}
So let's go ahead and register them all:
private Container ContainerFactory()
{
var container = new Container();
container.Register<ISettings, GoodSettings>();
container.RegisterAll<IOneOfMany>(this.GetAllOfThem(container));
container.Register<IOneOfMany>(() => this.GetTheOneIWant(container));
return container;
}
private IEnumerable<Type> GetAllOfThem(Container container)
{
var types = OpenGenericBatchRegistrationExtensions
.GetTypesToRegister(
container,
typeof(IOneOfMany),
AccessibilityOption.AllTypes,
typeof(IOneOfMany).Assembly);
return types;
}
The magic happens in the call to GetTheOneIWant - this is a delegate and will not get called until after the Container configuration has completed - here's the logic for the delegate:
private IOneOfMany GetTheOneIWant(Container container)
{
var settings = container.GetInstance<ISettings>();
var result = container
.GetAllInstances<IOneOfMany>()
.SingleOrDefault(i => i.GetType().Name == settings.IWantThisOnePlease);
return result;
}
A simple test will confirm it works as expected:
[Test]
public void Container_RegisterAll_ReturnsTheOneSpecifiedByTheSettings()
{
var container = this.ContainerFactory();
var result = container.GetInstance<IOneOfMany>();
Assert.That(result, Is.Not.Null);
}

As you already stated, Simple Injector does not allow mixing registration and resolving instances. When the first type is resolved from the container, the container is locked for further changes. When a call to one of the registration methods is made after that, the container will throw an exception. This design is chosen to force the user to strictly separate the two phases, and prevents all kinds of nasty concurrency issues that can easily come otherwise. This lock down however also allows performance optimizations that make Simple Injector the fastest in the field.
This does however mean that you sometimes need to think a little bit different about doing your registrations. In most cases however, the solution is rather simple.
In your example for instance, the problem would simply be solved by letting the ISomeOtherService implementation have a constructor argument of type ISettings. This would allow the settings instance to be injected into that type when it is resolved:
container.Register<ISettings, Settings>();
container.Register<ISomeOtherService, SomeOtherService>();
// Example
public class SomeOtherService : ISomeOtherService {
public SomeOtherService(ISettings settings) { ... }
}
Another solution is to register a delegate:
container.Register<ISettings, Settings>();
container.Register<ISomeOtherService>(() => new SomeOtherService(
container.GetInstance<ISettings>().Value));
Notice how container.GetInstance<ISettings>() is still called here, but it is embedded in the registered Func<ISomeOtherService> delegate. This will keep the registration and resolving separated.
Another option is to prevent having a large application Settings class in the first place. I experienced in the past that those classes tend to change quite often and can complicate your code because many classes will depend on that class/abstraction, but every class uses different properties. This is an indication of a Interface Segregation Principle violation.
Instead, you can also inject configuration values directly into classes that require it:
var conString = ConfigurationManager.ConnectionStrings["Billing"].ConnectionString;
container.Register<IConnectionFactory>(() => new SqlConnectionFactory(conString));
In the last few application's I built, I still had some sort of Settings class, but this class was internal to my Composition Root and was not injected itself, but only the configuration values it held where injected. It looked like this:
string connString = ConfigurationManager.ConnectionStrings["App"].ConnectionString;
var settings = new AppConfigurationSettings(
scopedLifestyle: new WcfOperationLifestyle(),
connectionString: connString,
sidToRoleMapping: CreateSidToRoleMapping(),
projectDirectories: ConfigurationManager.AppSettings.GetOrThrow("ProjectDirs"),
applicationAssemblies:
BuildManager.GetReferencedAssemblies().OfType<Assembly>().ToArray());
var container = new Container();
var connectionFactory = new ConnectionFactory(settings.ConnectionString);
container.RegisterSingle<IConnectionFactory>(connectionFactory);
container.RegisterSingle<ITimeProvider, SystemClockTimeProvider>();
container.Register<IUserContext>(
() => new WcfUserContext(settings.SidToRoleMapping), settings.ScopedLifestyle);
UPDATE
About your update, if I understand correctly, you want to allow the registered type to change based on a configuration value. A simple way to do this is as follows:
var settings = new Settings();
container.RegisterSingle<ISettings>(settings);
Type theTypeWeWantToRegister = Type.GetType(settings.GetTheISomeOtherServiceType());
container.Register(typeof(ISomeOtherService), theTypeWeWantToRegister);
But please still consider not registering the Settings file at all.
Also note though that it's highly unusual to need that much flexibility that the type name must be placed in the configuration file. Usually the only time you need this is when you have a dynamic plugin model where a plugin assembly can be added to the application, without the application to change.
In most cases however, you have a fixed set of implementations that are already known at compile time. Take for instance a fake IMailSender that is used in your acceptance and staging environment and the real SmptMailSender that is used in production. Since both implementations are included during compilation, allowing to specify the complete fully qualified type name, just gives more options than you need, and means that there are more errors to make.
What you just need in that case however, is a boolean switch. Something like
<add key="IsProduction" value="true" />
And in your code, you can do this:
container.Register(typeof(IMailSender),
settings.IsProduction ? typeof(SmtpMailSender) : typeof(FakeMailSender));
This allows this configuration to have compile-time support (when the names change, the configuration still works) and it keeps the configuration file simple.

How do you alternate Ninject bindings based on user?

This question requires a bit of context before it makes sense so I'll just start with a description of the project.
Project Background
I have an open source project which is a command-prompt style website (U413.com, U413.GoogleCode.com). This project is built in ASP.NET MVC 3 and uses Entity Framework 4. Essentially the site allows you to pass in commands and arguments and then the site returns some data. The concept is fairly simple, but I didn't want to use one giant IF statement to handle the commands. Instead, I decided to do something somewhat unique and build an object that contains all the possible commands as methods on the object.
The site uses reflection to locate methods that correspond to the sent command and execute them. This object is built dynamically based on the current user because some users have access to different commands than other users (e.g. Administrators have more than moderators, and mods have more than users, etc, etc).
I built a custom CommandModuleFactory that would be created in the MVC controller and would call it's BuildCommandModule method to build out a command module object. I am now using Ninject for dependency injection and I want to phase out this CommandModuleFactory, in favor of having the ICommandModule injected into the controller without the controller doing any work.
ICommandModule has one method defined, like this:
public interface ICommandModule
{
object InvokeCommand(string command, List<string> args);
}
InvokeCommand is the method that performs the reflection over itself to find all methods that might match the passed in command.
I then have five different objects that inherit from ICommandModule (some of them inherit from other modules as well so we don't repeat commands):
AdministratorCommandModule inherits from ModeratorCommandModule which inherits from UserCommandModule which inherits from BaseCommandModule.
I then also have VisitorCommandModule which inherits from BaseCommandModule because visitors will not have access to any of the commands in the other three command modules.
Hopefully you can start to see how this works. I'm pretty proud of the way this is all working so far.
The Question
I want Ninject to build my command module for me and bind it to ICommandModule so that I can just make my MVC controller dependent upon ICommandModule and it will receive the correct version of it. Here is what my Ninject module looks like where the binding takes place.
public class BuildCommandModule : NinjectModule
{
private bool _isAuthenticated;
private User _currentUser;
public BuildCommandModule(
bool isAuthenticated,
string username,
IUserRepository userRepository
)
{
this._isAuthenticated = isAuthenticated;
this._currentUser = userRepository.GetUserBy_Username(username);
}
public override void Load()
{
if (_isAuthenticated)
if (_currentUser.Administrator)
//load administrator command module
this.Bind<ICommandModule>().To<AdministratorCommandModule>();
else if (_currentUser.Moderator)
//Load moderator command module
this.Bind<ICommandModule>().To<ModeratorCommandModule>();
else
//Load user command module
this.Bind<ICommandModule>().To<UserCommandModule>();
else
//Load visitor command module
this.Bind<ICommandModule>().To<VisitorCommandModule>();
}
}
A couple things are happening here. Firstly, the Ninject module depends on a few things. It depends on a boolean indicating whether or not the user is authenticated (to determine if it will be one of the logged in command modules, or the visitor command module). Next it depends on a string username and IUserRepository. Here is where my mappings are defined in Global.asax.
protected override IKernel CreateKernel()
{
var kernel = new StandardKernel();
kernel.Bind<IBoardRepository>().To<BoardRepository>();
kernel.Bind<IReplyRepository>().To<ReplyRepository>();
kernel.Bind<ITopicRepository>().To<TopicRepository>();
kernel.Bind<IUserRepository>().To<UserRepository>();
kernel.Load(new BuildCommandModule(User.Identity.IsAuthenticated, User.Identity.Name, kernel.Get<IUserRepository>()));
return kernel;
}
You can see that I map IUserRepository to its concrete type before I load the Ninject module to build my command module (try not to confuse Ninject binding modules with my command modules :S). I then use kernel.Get<IUserRepository>() to resolve my Ninject module's dependency on it.
My problem here is that HttpContext.Current.User is null. I'm not sure how to tell whether or not a user is logged in during the Ninject binding phase. Any ideas?
How might I get reference to the logged in user when I'm doing my Ninject bindings? Or can you think of a better way for me to do conditional binding for my ICommandModule?

You should use a provider instead of putting the logic in your module. First you can create something like a SecurityInformation class that can tell you whether the user is authenticated and their role. Currently your implementation I think only uses the authorization information of the first user to start the app. However you want to check the current user's permissions every time an instance of this module is requested.
public class CommandModuleProvider : IProvider
{
public Type Type { get { return typeof(ICommandModule); } }
public object Create(IContext context)
{
var securityInfo = context.Kernel.Get<SecurityInformation>();
if (securityInfo.IsAuthenticated)
if (securityInfo.IsCurrentUserAdministrator)
//load administrator command module
return context.Kernel.Get<AdministratorCommandModule>();
else if (securityInfo.IsCurrentUserModerator)
//Load moderator command module
return context.Kernel.Get<ModeratorCommandModule>();
else
//Load user command module
return context.Kernel.Get<UserCommandModule>();
else
//Load visitor command module
return context.Kernel.Get<VisitorCommandModule>();
}
}
The binding would then be specified like
Kernel.Bind<ICommandModule>().ToProvider<CommandModuleProvider>();

There should be a (very) limited number of Kernels running in your application: preferably just one in most cases. Instead of trying to create a new kernel for each user, make your binding produce a different implementation for each user. This can be done using IProviders as Vadim points out. Following is a variation on the same idea:
public override void Load()
{
Bind<ICommandModule>().ToMethod(
c =>
{
var sessionManager = c.Kernel<ISessionManager>();
if (!sessionManager.IsAuthenticated)
return c.Kernel.Get<VisitorCommandModule>();
var currentUser = sessionManager.CurrentUser;
if (currentUser.IsAdministrator)
return c.Kernel.Get<AdministratorCommandModule>();
if (currentUser.IsModerator)
return c.Kernel.Get<ModeratorCommandModule>();
return c.Kernel.Get<UserCommandModule>();
}).InRequestScope();
}
In this implementation, I would expect ISessionManager to be implemented with a class that checks the current HttpContext to determine who is logged in, and provide basic information about this person.
InRequestScope() now resides in the Ninject.Web.Common library, and will help to avoid re-performing all this logic more than once per request.