What is the purpose of the extension method CreatePerOwinContext in OWIN implementation by Microsoft

Next Developer picture Next Developer · Oct 29, 2014 · Viewed 20.7k times · Source

I am a newbie in ASP.NET, and currently learning ASP.NET Identity. I know it's built on top of OWIN implementation by Microsoft, and I am also still learning that too. So, I came across the extension method CreatePerOwinContext in the Owin startup code, and I don't see a clear purpose of using it. Is it some kind of dependency injection container? What is the real purpose of the method? In what case it should be applied?

Answer

LeftyX picture LeftyX · Oct 29, 2014

CreatePerOwinContext registers a static callback which your application will use to get back a new instance of a specified type.
This callback will be called once per request and will store the object/objects in OwinContext so that you will be able to use them throughout the application.

Let's say you have defined your own implementation of IdentityDbContext:

public class ApplicationDatabaseContext : IdentityDbContext<MyApplicationUser, MyRole, Guid, MyUserLogin, MyUserRole, MyUserClaim>
{
    public ApplicationDatabaseContext() : base("<connection string>")
    {
    }

    public static ApplicationDatabaseContext Create()
    {
        return new ApplicationDatabaseContext();
    }

        protected override void OnModelCreating(System.Data.Entity.DbModelBuilder modelBuilder)
        {
        base.OnModelCreating(modelBuilder);

        // Customize your table creation here.

            #region USERS - INFOS

        modelBuilder.Entity<UserInfo>()
            .Property(p => p.FirstName)
            .HasColumnType("varchar")
            .HasMaxLength(70);

        modelBuilder.Entity<UserInfo>()
            .Property(p => p.LastName)
            .HasColumnType("varchar")
            .HasMaxLength(70);

        modelBuilder.Entity<UserInfo>()
            .Property(p => p.Address)
            .HasColumnType("varchar")
            .HasMaxLength(100);

        modelBuilder.Entity<UserInfo>()
            .Property(p => p.City)
            .HasColumnType("varchar")
            .HasMaxLength(100);

        modelBuilder.Entity<UserInfo>()
            .ToTable("UsersInfo");

        #endregion  
        }

        public DbSet<UserInfo> UsersInfo { get; set; }
}

and your implementation of UserManager:

public class ApplicationUserManager : UserManager<MyApplicationUser, Guid>
{
    public ApplicationUserManager(IUserStore<MyApplicationUser, Guid> store) : base(store)
        {
        }

        public static ApplicationUserManager Create(IdentityFactoryOptions<ApplicationUserManager> options, IOwinContext context)
        {
            var manager = new ApplicationUserManager(new MyUserStore(context.Get<ApplicationDatabaseContext>()));

            manager.UserValidator = new UserValidator<MyApplicationUser, Guid>(manager)
            {
                AllowOnlyAlphanumericUserNames = false,
                RequireUniqueEmail = true
            };

            manager.PasswordValidator = new PasswordValidator()
            {
                RequiredLength = 6,
                RequireNonLetterOrDigit = false,    
                // RequireDigit = true,
                RequireLowercase = false,
                RequireUppercase = false,
            };

            var dataProtectionProvider = options.DataProtectionProvider;

            if (dataProtectionProvider != null)
            {
                manager.UserTokenProvider = new DataProtectorTokenProvider<MyApplicationUser, Guid>(dataProtectionProvider.Create("PasswordReset"));
            }

            return (manager);
        }
}

In your Owin Startup you will register the callback:

// IAppBuilder app

app.CreatePerOwinContext<ApplicationDatabaseContext>(ApplicationDatabaseContext.Create);
app.CreatePerOwinContext<ApplicationUserManager>(ApplicationUserManager.Create);

which will call the static method:

public static ApplicationDatabaseContext Create()
{
    return new ApplicationDatabaseContext();
}

and

public static ApplicationUserManager Create(IdentityFactoryOptions<ApplicationUserManager> options, IOwinContext context)
{
    ...
}

Now you will be able to access your database context and user manager in a simple straightforward way:

ApplicationDatabaseContext dbContext = context.OwinContext.Get<ApplicationDatabaseContext>();
ApplicationUserManager userManager = context.OwinContext.GetUserManager<ApplicationUserManager>();

In your ApiController (if you're using WebApi):

IAuthenticationManager authenticationManager = HttpContext.Current.GetOwinContext().Authentication;
ApplicationUserManager applicationUserManager = HttpContext.Current.GetOwinContext().GetUserManager<ApplicationUserManager>();