I wish to implement OWIN as per the example I could find here: http://www.asp.net/web-api/overview/security/individual-accounts-in-web-api

However, since this way of working is new to me especially using my self created database I would like some guidance. I can submit my registration request without a problem.

The post takes me to the AccountController:

    [AllowAnonymous]
    [Route("Register")]
    public async Task<IHttpActionResult> Register(RegisterBindingModel model)
    {
        if (!ModelState.IsValid)
        {
            return BadRequest(ModelState);
        }

        try { 
            var email = model.Email;
            var password = model.Password;

            var user = new users() {
                 Email = email,
                 PasswordHash = password,
                 Password = password
            };

            IdentityResult result = await UserManager.CreateAsync(user, model.Password);

            if (!result.Succeeded)
            {
                return GetErrorResult(result);
            }

            return Ok();
        }
        catch(Exception ex)
        {
            throw;
        }
    }

This triggers the below code:

    public ApplicationUserManager UserManager
    {
        get
        {
            return _userManager ?? Request.GetOwinContext().GetUserManager<ApplicationUserManager>();
        }
        private set
        {
            _userManager = value;
        }
    }

ApplicationUserManager:

public class ApplicationUserManager : UserManager<users>
{
    public ApplicationUserManager(IUserStore<users> store)
        : base(store)
    {
    }

    public static ApplicationUserManager Create(IdentityFactoryOptions<ApplicationUserManager> options, IOwinContext context)
    {
        var manager = new ApplicationUserManager(new UserStore<users>(context.Get<DaumAuctionEntities>()));
        var dataProtectionProvider = options.DataProtectionProvider;

        // Configure validation logic for passwords
        manager.PasswordValidator = new PasswordValidator
        {
            RequiredLength = 6,
            RequireNonLetterOrDigit = false,
            RequireDigit = false,
            RequireLowercase = true,
            RequireUppercase = true,
        };

        if (dataProtectionProvider != null)
        {
            manager.UserTokenProvider = new DataProtectorTokenProvider<users>(dataProtectionProvider.Create("ASP.NET Identity"));
        }

        return manager;
    }
}

But for some weird reason I'm getting

 modelState: {undefined: ["Name cannot be null or empty."]}

Even though I don't use name anywhere?! Where is this name coming from?

So I presume I'm doing something wrong but it's hard to debug without a clear explanation on how to implement OWIN with an existing DB.

Below my context/entity and users table that I would like to use to store me user data.

context:

public partial class DaumAuctionEntities : IdentityDbContext<users>
{
    public DaumAuctionEntities()
        : base("name=DaumAuctionEntities")
    {
    }

    public DbSet<addresses> addresses { get; set; }
    public DbSet<auctions> auctions { get; set; }
    public DbSet<images> images { get; set; }
    public DbSet<users> users { get; set; }
}

users : IdentityUser:

public partial class users : IdentityUser
{
    public override string UserName
    {
        get
        {
            return Email;
        }
        set
        {
            Email = value;
        }
    }

    override public string PasswordHash
    {
        get
        {
            return Password;
        }

        set
        {
            Password = value;
        }
    }

    public async Task<ClaimsIdentity> GenerateUserIdentityAsync(UserManager<users> manager, string authenticationType)
    {
        // Note the authenticationType must match the one defined in CookieAuthenticationOptions.AuthenticationType
        var userIdentity = await manager.CreateIdentityAsync(this, authenticationType);
        // Add custom user claims here
        return userIdentity;
    }
}

public partial class users
{
    public int Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public System.DateTime CreatedDate { get; set; }
    public Nullable<System.DateTime> ModifiedDate { get; set; }

}

Edit:

If I add UserName back to my new users object before I try to call CreateAsync, the error is gone but I get another one instead:

"The specified type member 'UserName' is not supported in LINQ to Entities. Only initializers, entity members, and entity navigation properties are supported."

Edit II:

I also have this issue in the tutorial code! This is just a freaking bug in .NET?

Edit III

I tried to do an override as you can see in the partial class Users above. But I still have the same error.