Usermanager with model inherited from applicationUser - entity-framework

Question

I'm early beginner in ASP.NET, and I'm trying to build user system using Identity framework in ASP.NET-MVC project.
I want to have "Admin" user entity inherit from base entity "applicationUser" which is created by default in my models (with my minor changes):
public class ApplicationUser : IdentityUser
{
[Required]
[StringLength(50)]
[Display(Name = "Last Name")]
public string LastName { get; set; }
[Required]
[StringLength(50, ErrorMessage = "First name cannot be longer than 50 characters.")]
[Column("FirstName")]
[Display(Name = "First Name")]
public string FirstMidName { get; set; }
[Display(Name = "Full Name")]
public string FullName
{
get
{
return LastName + ", " + FirstMidName;
}
}
}
public class Admin: ApplicationUser
{
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int AdID;
}
I will also add 2 other inheritance from applicationUser, I want to have separeted models for different users to store different information in their database fileds and let all of them login to my site.
In startup I'm trying to initially add admin user using this code (taken somewhere in stackoverflow answers):
public static async Task CreateRoles(SchoolContext context, IServiceProvider serviceProvider)
{
var userManager = serviceProvider.GetRequiredService<UserManager<ApplicationUser>>();
var roleManager = serviceProvider.GetRequiredService<RoleManager<IdentityRole>>();
// First, Creating User role as each role in User Manager
List<IdentityRole> roles = new List<IdentityRole>();
roles.Add(new IdentityRole { Name = "Student", NormalizedName = "STUDENT" });
roles.Add(new IdentityRole { Name = "ADMIN", NormalizedName = "ADMINISTRATOR" });
roles.Add(new IdentityRole { Name = "Professor", NormalizedName = "PROFESSOR" });
//Then, the machine added Default User as the Admin user role
foreach (var role in roles)
{
var roleExit = await roleManager.RoleExistsAsync(role.Name);
if (!roleExit)
{
context.Roles.Add(role);
context.SaveChanges();
}
}
await CreateUser(context, userManager);
}
private static async Task CreateUser(SchoolContext context, UserManager<ApplicationUser> userManager)
{
var adminUser = await userManager.FindByEmailAsync("alpha#lms.com");
if (adminUser != null)
{
if (!(await userManager.IsInRoleAsync(adminUser, "ADMINISTRATOR")))
await userManager.AddToRoleAsync(adminUser, "ADMINISTRATOR");
}
else
{
var newAdmin = new applicationUser()
{
UserName = "alpha#lms.com",
Email = "alpha#lms.com",
LastName = "Admin",
FirstMidName = "Admin",
};
var result = await userManager.CreateAsync(newAdmin, "password123;");
if (!result.Succeeded)
{
var exceptionText = result.Errors.Aggregate("User Creation Failed
- Identity Exception. Errors were: \n\r\n\r",
(current, error) => current + (" - " + error + "\n\r"));
throw new Exception(exceptionText);
}
await userManager.AddToRoleAsync(newAdmin, "ADMINISTRATOR");
}
}
But when I try to do it, I receive an exception:
"Cannot insert the value NULL into column 'Discriminator', table 'aspnet-University; column does not allow nulls. INSERT fails.
The statement has been terminated."
If I try to change variable Admin type on "new Admin" instead of "new applicationUser", I receive another exception:
The entity type 'Admin' was not found. Ensure that the entity type has been added to the model.
I know that this question is about basics of identity framework; I do not understand them well yet; I've just began to understand it's prinicples and I don't know how to handle my problem.
My guess that I need to create New UserManager, which will be able to manipulate instances which inherit from basic applicationUser model. I will be happy if you recommend me relevant resources on this topic and help me solve my problem.

Answer 1

In case if anyone will have this question - I've decided not to use inheritance from ApplicationUser, because it obviously was wrong approach, instead and inherit all custom user models from IdentityUser class. To make this work I've added to StartUp Configure services this lines:
services.AddIdentity <IdentityUser, IdentityRole>()
.AddEntityFrameworkStores<YourContext>()
.AddDefaultTokenProviders();
My user model declared like this:
public class Admin : IdentityUser
{
}
And in context file I have this:
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<IdentityUser>(i => {
i.ToTable("Users");
i.HasKey(x => x.Id);
});
modelBuilder.Entity<IdentityRole<>(i => {
i.ToTable("Role");
i.HasKey(x => x.Id);
});
}
With this code I can use Identity's UserManager and RoleManager without additional changes.