Understanding Asp.Net Identity key points

Question

I am an Asp.net developer but very much new to the Asp.net Identity framework. I have been studying the sample application and followed some tutorials too on Identity but still I am not able to grasp the concept completely. I have very firm grip over Asp.net membership but Identity seems nothing like membership. I will explain what I have done so far.

I am creating a simple application in which I am following code first approach. I have created entity model for User which inherits from IdentityUser and has some extra fields. Below is entity model for User.

public class User : IdentityUser
{
    public int? CompanyID { get; set; }

    public bool? CanWork { get; set; }

    public bool? CanSearch { get; set; }

    public Company Company { get; set; }
}

Now in the examples people use the name ApplicationUser but for my own purpose I have used name User. Also there is a method in User or ApplicationUser model which is,

public async Task<ClaimsIdentity> GenerateUserIdentityAsync(UserManager<User> manager)
    {
        CookieAuthenticationOptions.AuthenticationType
        var userIdentity = await manager.CreateIdentityAsync(this, DefaultAuthenticationTypes.ApplicationCookie);
        // Add custom user claims here
        return userIdentity;
    }

I am unable to understand the purpose of this method. Also from an example I have used the following model for Role,

public class Role : IdentityRole
{
    public Role()
    {

    }

    public Role(string roleName, string description)
        : base(roleName)
    {
        this.Description = description;
    }

    public string Description { get; set; }
}

I understand that an extra field is added but I am unable to understand the purpose of overloaded constructor.

The above mentioned confusions are secondary. My primary confusion is that I am familiar that when I create entity models I use DbSet and DbContext and when I call any entity framework method to access the database, the database is created/drop created whichever scheme I am following.

In Identity which method is responsible for creating the Identity tables in the database? I have a IdentityConfig file in which I declare ApplicationUserManager and ApplicationSignInManager. I have also a Startup file. Previously I had only one Startup file in the App_Start folder and when I run the application and tried to accessed any Identity methods it gave me error and was not creating database. I then made the class as partial and created another partial class with same name at the root and then the exception was gone and tables were created. So Startup class is responsible for creating Identity tables? There are extra columns created automatically in the AspNetUsers like PhoneNumber, PhoneNumberConfirmed, TwoFactorEnabled. I don't need these extra columns. Can I remove these? Can I change the names of the Identity tables that are created?

I know these are very basic questions and not one question at all but if I was unable to find some basic tutorial or example for beginners then it would be very beneficial. What I have found are describing those things which I don't need or making me confuse. I want to understand and have control how Identity should work in my application but till now it seems to me that neither I am grasping it completely and nor being able to make is adjustable to my needs. Its like tutorials and example are teaching me how to make sentences but I am unable to understand the alphabets. :(

Answer 1

First of all you have to define the model - as you're doing - implementing the right interfaces.
Let's say you want to create a user for your application:

public class MyUser : IdentityUser<string, MyUserLogin, MyUserRole, MyUserClaim>
{
    public string CompanyName { get; set; }
}

As you can see I've implemented the IdentityUser interface (namespace Microsoft.AspNet.Identity.EntityFramework).

I've specified what type of identifier I want to use for my primary key (string) and included my custom objects to manges login, roles and claims.

Now we can defined the role object:

public class MyRole : IdentityRole<string, MyUserRole>
{
}

Again there's a type and the class I've defined for the management of users belonging to to a role.

public class MyUserRole : IdentityUserRole<string>
{
}

MyUserLogin is going to implement IdentityUserLogin<string>.
MyUserClaim is going to implement IdentityUserClaim<string>.

As you can see each interface need a type for the primary key.

The second step is to create the user store:

public class MyUserStore:  UserStore<MyUser, MyRole, string, MyUserLogin, MyUserRole, MyUserClaim>
{
    public MyUserStore(MyContext context)
        : base(context)
    {
    }
}

Again we have defined what user, role, login etc etc we want to use.
We need UserStore cause our UserManager is going to need one.

If you're planning to manage roles and associate roles with each user you have to create your RoleStore definition.

public class MyRoleStore : RoleStore<MyRole, string, MyUserRole>
{
    public DaufRoleStore(ApplicationDatabaseContext context) : base(context)
    {
    }
}

Now you can create your UserManager. The UserManager is the real responsible of saving changes to the UserStore.

public class ApplicationUserManager : UserManager<MyUser, string>
{
    public ApplicationUserManager(IUserStore<MyUser, string> store)
        : base(store)
    {

    }

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

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

        manager.PasswordValidator = new PasswordValidator()
        {
        RequiredLength = 5,
        RequireNonLetterOrDigit = false,     // true
        // RequireDigit = true,
        RequireLowercase = false,
        RequireUppercase = false,
        };

        return (manager);
    }
}

This class has a static method which will create a new UserManager for you.
Interesting to note that you can include some validation rules you might need to validate password etc etc.

Last thing is to create or database context.

public class MyContext : IdentityDbContext<MyUser, MyRole, string, MyUserLogin, MyUserRole, MyUserClaim>
{
    public MyContext(): base("<your connection string here>")
    {

    }

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

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

        modelBuilder.Entity<MyUser>()
            .ToTable("Users");

        modelBuilder.Entity<MyRole>()
            .ToTable("Roles");

        modelBuilder.Entity<MyUserRole>()
            .ToTable("UserRoles");

        modelBuilder.Entity<MyUserClaim>()
            .ToTable("UserClaims");

        modelBuilder.Entity<MyUserLogin>()
            .ToTable("UserLogins");
    }
}

As you can see I've used the model builder to change the names all the tables. You can define keys or fields type or tables relations here.

This is the place where you're going to attach your custom classes you want to manage in your context:

public DbSet<MyCustomer> Customers{ get; set; }

Again MyContext has a Create method which returns a new context:

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

Now you should have a startup class where you're going to bootstrap your stuff:

[assembly: OwinStartup(typeof(ASPNETIdentity2.Startup))]

namespace ASPNETIdentity2
{
    public class Startup
    {
        public void Configuration(IAppBuilder app)
        {
            app.CreatePerOwinContext(MyContext.Create);
            app.CreatePerOwinContext<ApplicationUserManager>(ApplicationUserManager.Create);
        }
    }
}

Here you're going to create your database context and your user manager you can use in your application.

Notice the first line:

[assembly: OwinStartup(typeof(ASPNETIdentity2.Startup))]

This is needed cause you're telling your environment that is the startup class which needs to be called at ... startup.

Now in your controllers you can simply refer to your UserManager doing something like this:

HttpContext.GetOwinContext().GetUserManager<ApplicationUserManager>();

How can you create your tables?

In Visual Studio go to TOOLS -> NuGet Packager Manager -> Package Manager Console.

In the window there's a combobox "Default Project". Choose your ASP.NET MVC project.
Run this command:

Enable-Migrations

It will create a file Configuration.cs in a new folder called Migrations.
If you want to create your database you need to open that file and change the AutomaticMigrationsEnabled to true:

public Configuration()
{
    AutomaticMigrationsEnabled = true;
}

Again, from Package Manager Console, you can run:

Update-Database

and all your tables will appear in your database. Don't forget your connection string.

You can download this github project to see how everything works.
You can check these two answers with some other info.

The first of the two has got some links to a blog where you can learn all these things.

NOTE:

You have to do all this if you want to customized every single bit of your environment.