How to Seed Users and Roles with Code First Migration using Identity ASP.NET Core

I have created a new clean asp.net 5 project (rc1-final). Using Identity Authentication I just have the ApplicationDbContext.cs with the following code:

public class ApplicationDbContext : IdentityDbContext<ApplicationUser>
{
    protected override void OnModelCreating(ModelBuilder builder)
    {
        // On event model creating
        base.OnModelCreating(builder);
    }
}

Please note ApplicationDbContext use IdentityDbContext and not DbContext.

There is any IdentityConfig.cs. Where i need to put the classic protected override void Seed to create role and user if it does not exist?

My way of doing this is to create a class in models namespace.

public class SampleData
{
    public static void Initialize(IServiceProvider serviceProvider)
    {
        var context = serviceProvider.GetService<ApplicationDbContext>();

        string[] roles = new string[] { "Owner", "Administrator", "Manager", "Editor", "Buyer", "Business", "Seller", "Subscriber" };

        foreach (string role in roles)
        {
            var roleStore = new RoleStore<IdentityRole>(context);

            if (!context.Roles.Any(r => r.Name == role))
            {
                roleStore.CreateAsync(new IdentityRole(role));
            }
        }


        var user = new ApplicationUser
        {
            FirstName = "XXXX",
            LastName = "XXXX",
            Email = "xxxx@example.com",
            NormalizedEmail = "XXXX@EXAMPLE.COM",
            UserName = "Owner",
            NormalizedUserName = "OWNER",
            PhoneNumber = "+111111111111",
            EmailConfirmed = true,
            PhoneNumberConfirmed = true,
            SecurityStamp = Guid.NewGuid().ToString("D")
        };


        if (!context.Users.Any(u => u.UserName == user.UserName))
        {
            var password = new PasswordHasher<ApplicationUser>();
            var hashed = password.HashPassword(user,"secret");
            user.PasswordHash = hashed;

            var userStore = new UserStore<ApplicationUser>(context);
            var result = userStore.CreateAsync(user);

        }

        AssignRoles(serviceProvider, user.Email, roles);

        context.SaveChangesAsync();
    }

    public static async Task<IdentityResult> AssignRoles(IServiceProvider services, string email, string[] roles)
    {
        UserManager<ApplicationUser> _userManager = services.GetService<UserManager<ApplicationUser>>();
        ApplicationUser user = await _userManager.FindByEmailAsync(email);
        var result = await _userManager.AddToRolesAsync(user, roles);

        return result;
    }

}

To run this code on startup. In Startup.cs at end of configure method just after route configuration add following code as Stafford Williams said before.

SampleData.Initialize(app.ApplicationServices);