How can I make a foreign key relationship between an identity server column and another custom table? - asp.net-core

Question

I use identity server.
I know that if I want to add new columns, I make a new class which will inherit from IdentityUser, and in SQL Server with EF, the column will be generated. But I want to have a "Gender" column which will have a foreign key relationship with another custom-made table: "1" will be for "male", "2" for "female" etc.
I also want to make a similar relationship with another table where the programming languages of every employee will be stored.
Is that possible?
public ApplicationUser : IdentityUser
{
public string FullName {get ; set; }
public int GenderId { get ; set ;}
public ICollection<ProgrammingLanguages> PL {get ; set ;}
}

Answer 1

Basically you need to implement one-to-many relationship between User and Gender tables and many-to-many relationship between User and ProgrammingLanguage. Many-to-many relationship requires extra table which will contain foreign keys to User and ProgrammingLanguage tables. You then need to override OnModelCreating() method and don't forget to call the base implementation of OnModelCreating() method so that let the base implementation to setup relationships between identity tables. You can read more on how to implement relationships between entities here. Here is the sample code how this can be done:
public ApplicationUser : IdentityUser
{
public string FullName { get; set; }
public int GenderId { get; set; }
public Gender Gender { get; set; }
public ICollection<UserProgrammingLanguage> UserProgrammingLanguages { get; set;}
}
public class ProgrammingLanguage
{
public int Id { get; set; }
public string Name { get; set; }
}
public class UserProgrammingLanguage
{
public string UserId { get; set; }
public ApplicationUser User { get; set; }
public int ProgrammingLanguageId { get; set; }
public ProgrammingLanguage ProgrammingLanguage { get; set; }
}
public class Gender
{
public int Id { get; set; }
public string Name { get; set; }
}
public class ApplicationContext : IdentityDbContext<ApplicationUser>
{
public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options)
: base(options)
{
}
public DbSet<Gender> Genders { get; set; }
public DbSet<ProgrammingLanguage> ProgrammingLanguages { get; set; }
protected override void OnModelCreating(ModelBuilder builder)
{
builder.Entity<UserProgrammingLanguage>(entity =>
{
entity.HasKey(pl => { pl.UserId, pl.ProgrammingLanguageId });
entity.HasOne(pl => pl.User)
.WithMany(u => u.UserProgrammingLanguages)
.HasForeignKey(pl => pl.UserId);
entity.HasOne(pl => pl.ProgrammingLanguage)
.WithMany()
.HasForeignKey(pl => pl.ProgrammingLanguageId);
}
builder.Entity<ApplicationUser>(entity =>
{
entity.HasOne(u => u.Gender)
.WithMany()
.HasForeignKey(u => u.GenderId)
.OnDelete(DeleteBehavior.Cascade);
})
base.OnModelCreating(builder);
}
}