How to inject UserManager & SignInManager

Prerequisites

Start a new MVC5 application using the MVC template. This will install all the necessary dependencies as well as deploy the Startup.Auth.cs file which contains the bootstrap code for Microsoft.AspNet.Identity (it als includes the all the references for Microsoft.AspNet.Identity).

Install the following packages and update them to the latest afterwards.

Install-Package Ninject
Install-Package Ninject.MVC5

Configuration

Remove the default constructor on the AccountController so only the parameterized constructor remains. It should have the follownig signature.

public AccountController(ApplicationUserManager userManager, ApplicationSignInManager signInManager)

This will ensure that you will get an error if injection fails which is what we want.

NInject Configuration

The NInject NuGet package deployment will have created a file named NinjectWebCommon.cs where the boiler plate NInject registration takes place. This has a method with the following signature which you can extend with your registrations.

private static void RegisterServices(IKernel kernel)

Now we will add the following code to this method to get NInject automatically inject the ApplicationSignInManager and ApplicationUserManager instances.

private static void RegisterServices(IKernel kernel) {
    kernel.Bind<IUserStore<ApplicationUser>>().To<UserStore<ApplicationUser>>();
    kernel.Bind<UserManager<ApplicationUser>>().ToSelf();

    kernel.Bind<HttpContextBase>().ToMethod(ctx => new HttpContextWrapper(HttpContext.Current)).InTransientScope();

    kernel.Bind<ApplicationSignInManager>().ToMethod((context)=>
    {
        var cbase = new HttpContextWrapper(HttpContext.Current);
        return cbase.GetOwinContext().Get<ApplicationSignInManager>();
    });

    kernel.Bind<ApplicationUserManager>().ToSelf();
}

Thats it. Now you should be able to navigate to the Login or Register links and injection will occur.

Alternate Approach

I prefer a Proxy approach that exposes limited functionality for the ApplicationSignInManager and the ApplicationUserManager instances. I then inject this proxy into the necessary controllers. It helps abstract some of the Identity information away from the controllers which makes it easier to change in the future. This is not a new concept by any means and whether you do this or not depends on the size and complexity of your project as well as how you want to handle dependencies. So the benefits are (common actually for any proxy):

• You can abstract some of the dependencies away from your code
• You can streamline some of the calls within the api
• You can expose only that functionality that you want to use including configurable parts
• Change management should be easier if the interfaces ever change, now you change the calls in your proxy instead of all the calling code across your controllers.

Code example:

public interface IAuthManager
{
    Task<SignInStatus> PasswordSignInAsync(string userName, string password, bool rememberMe);
}

public class AuthManager : IAuthManager
{
    private ApplicationUserManager _userManager;
    ApplicationSignInManager _signInManager;

    public AuthManager(ApplicationUserManager userManager, ApplicationSignInManager signInManager)
    {
        this._userManager = userManager;
        this._signInManager = signInManager;
    }

    public Task<SignInStatus> PasswordSignInAsync(string userName, string password, bool rememberMe)
    {
        return _signInManager.PasswordSignInAsync(userName, password, rememberMe, true);
    }
}

Add the following line in your NInject dependency registration.

kernel.Bind<IAuthManager>().To<AuthManager>();

Alter your AccountController constructor to take in an instance of IAuthManager. Finally change your methods to refer to this proxy instead of the ASP.NET Identity classes directly.

Disclaimer – I did not wire up a complex call, just a very simple one to illustrate my point. This is also entirely optional and whether you do it or not really should depend on the scope and size of your project and how you plan on using the ASP.NET Identity framework