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

Question

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 1

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>();