StructureMap, Web Api 2, and IUserStore error - dependency-injection

Question

I have just started experimenting with Web Api 2 and StructureMap, having installed StructureMap.MVC4 Nuget package. Everything seems to work fine until I tried to register a user. I got this error when this implementation of IHttpControllerActivator tried to instantiate a controller:
public class ServiceActivator : IHttpControllerActivator
{
public ServiceActivator(HttpConfiguration configuration) { }
public IHttpController Create(HttpRequestMessage request
, HttpControllerDescriptor controllerDescriptor, Type controllerType)
{
var controller = ObjectFactory.GetInstance(controllerType) as IHttpController;
return controller;
}
}
The error I got was:
StructureMap Exception Code: 202
No Default Instance defined for PluginFamily Microsoft.AspNet.Identity.IUserStore`1[[Microsoft.AspNet.Identity.EntityFramework.IdentityUser, Microsoft.AspNet.Identity.EntityFramework, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35]], Microsoft.AspNet.Identity.Core, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35
I understand what the error is, but not entirely sure how to solve it. Is it correct to assume the default scanner in StructureMap could not find a default implementation of IUserStore? Here's the initialisation code I used:
ObjectFactory.Initialize(x => x.Scan(scan =>
{
scan.AssembliesFromApplicationBaseDirectory();
scan.WithDefaultConventions();
}));
Any ideas please? Thanks.
EDIT:
I think I may have solved the initial issue using this:
x.For<Microsoft.AspNet.Identity.IUserStore<IdentityUser>>()
.Use<UserStore<IdentityUser>>();
But now there's another default instance StructureMap couldn't work out - the dbcontext. Here's the next error message I'm getting:
ExceptionMessage=StructureMap Exception Code: 202
No Default Instance defined for PluginFamily System.Data.Entity.DbContext, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
Now I'm really lost...

Answer 1

The WithDefaultConventions() call won't pick up your DbContext and AspNet Identity implementations. You'll want to look at some of the other methods like SingleImplementationsOfInterface() and ConnectImplementationsToTypesClosing.
By default when I setup my StructureMap container, I will do the following configuration in order to ensure that StructureMap will always resolve the interfaces and base classes of my preferred class to my actual preferred class:
ioc.For<MyDbContext>().HybridHttpOrThreadLocalScoped().Use<MyDbContext>();
ioc.For<DbContext>().HybridHttpOrThreadLocalScoped().Use<MyDbContext>();
For the new AspNet Identity classes, just subclass the generic classes they give you out of the box:
public class MyUserManager : UserManager<MyUser> { }
public class MyUserStore : UserStore<MyUser> { }
And then again, make sure StructureMap knows about these:
ioc.For<IUserStore<MyUser>>().Use<MyUserStore>();
ioc.For<UserStore<MyUser>>().Use<MyUserStore>();
ioc.For<UserManager<MyUser>>().Use<MyUserManager>();
Generally, you don't have to explicitly register every class with StructureMap, but with my DbContext and Identity classes, I prefer to have those explicity registered for maintenance purposes.

Answer 2

ericb: I can see the purpose of what you've posted but I can't quite get it to work. The MyUserManager class declaration "public class MyUserManager : UserManager { }" is complaining that the UserManager interface does not contain a constructor that takes 0 arguments?
Any help would be greatly appreciated!
Ps. This is by no means an answer but I'm not qualified enough to simply comment on your answer unfortunately!
Update: Found a solution here: Dependency Injection Structuremap ASP.NET Identity MVC 5
For clarity we replaced any of the above with the following in the IoC file:
x.For<Microsoft.AspNet.Identity.IUserStore<ApplicationUser>>()
.Use<Microsoft.AspNet.Identity.EntityFramework.UserStore<ApplicationUser>>();
x.For<System.Data.Entity.DbContext>().Use(() => new ApplicationDbContext());
I'm sure we're missing out on some extra benefits that ericb gets with his solution but we're not utilising anything that would take advantage of them.

Answer 3

There is a quick and easy workaround to this problem as well, and in many cases may be sufficient. Go to AccountController.cs and above the default constructor (the one with no params or code in it) add [DefaultConstructor] and resolve using structuremap.
[DefaultConstructor]
public AccountController()
{
}
Though the proper IoC solution is this...
For<IUserStore<ApplicationUser>>().Use<UserStore<ApplicationUser>>();
For<DbContext>().Use<ApplicationDbContext>(new ApplicationDbContext());
For<IAuthenticationManager>().Use(() => HttpContext.Current.GetOwinContext().Authentication);

Answer 4

Or you can try constructor injection method:
x.For<IUserStore<ApplicationUser>>().Use<UserStore<ApplicationUser>>()
.SelectConstructor(() => new UserStore<ApplicationUser>(new MyContext()));