Map relationships with Fluent API

Question

I have three simple classes of city, state and country. I realized that simply declaring a property of the type Estado in class Cidade the foreign key is generated correctly. I would like to know how to do these mappings in the hand, I am safer, and if my concern is not, is the doubt of the need to have the options to map in hand.

Follow the entities:

public class CidadeEntity {
    public int Id { get; set; }
    public string Nome { get; set; }
    //public int EstadoId { get; set; }
    public virtual EstadoEntity Estado { get; set; }
}

public class EstadoEntity{
    public int Id { get; set; }
    public string Sigla { get; set; }
    public string Nome { get; set; }
    public virtual IList<CidadeEntity> CidadeLista { get; set; }
    //public byte EstadoPaisId { get; set; }
    public virtual PaisEntity Pais { get; set; }
}

public class PaisEntity {
    public int Id { get; set; }
    public string Sigla { get; set; }
    public string Nome { get; set; }
    public virtual IList<EstadoEntity> EstadoLista { get; set; }
}

My mappings:

public CidadeMap() {
    ToTable("Cidade");
    HasKey(c => c.Id);
    Property(p => p.Nome)
        .IsRequired()
        .HasColumnType("varchar")
        .HasMaxLength(120);
    //HasRequired(f => f.Estado).WithMany(p => p.CidadeLista).HasForeignKey(p => p.EstadoId);
}

public EstadoMap() {
    ToTable("Estado");
    HasKey(c => c.Id);
    Property(p => p.Sigla).IsRequired().HasColumnType("char").HasMaxLength(5);
    Property(p => p.Nome).IsRequired().HasColumnType("varchar").HasMaxLength(75);
    //Ignore(p => p.EstadoPaisId);
    //Relacionamentos
    HasRequired(p => p.CidadeLista).WithRequiredPrincipal().Map(p => p.MapKey("EstadoId"));
}

public PaisMap() {
    ToTable("Pais");
    HasKey(c => c.Id);
    Property(p => p.Sigla)
        .HasColumnType("varchar")
        .HasMaxLength(5);
    Property(p => p.Nome)
        .HasColumnType("varchar")
        .HasMaxLength(50);
}

Context with BD:

[DbConfigurationType(typeof(MySql.Data.Entity.MySqlEFConfiguration))]    
public class DataContext:DbContext {
    public DataContext():base("ConexaoBD") {

    }

    public DbSet<PaisEntity> Pais { get; set; }

    public DbSet<EstadoEntity> Estado { get; set; }

    public DbSet<CidadeEntity> Cidade { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder) {
        modelBuilder.Configurations.Add(new PaisMap());
        modelBuilder.Configurations.Add(new EstadoMap());
        modelBuilder.Configurations.Add(new CidadeMap());
        base.OnModelCreating(modelBuilder);
    }
}

In the EstadoMap I mapped it with Cidade (HasRequired(p => p.CidadeLista).WithRequiredPrincipal().Map(p => p.MapKey("EstadoId"))) but it was duplicated because it generated mine and automatic mapping (this without nullable: false), I saw that you can do this mapping around the city too (HasRequired(p => p.Estado).WithRequiredDependent();), but it didn’t work out and I didn’t realize if there’s a difference between the State and the City. I don’t know if I’m doing things right.

Answer 1

So I made some adaptations mainly in your classes:

Cidademap

I kept

HasRequired(a => a.Estado).WithMany(a => a.CidadeLista).HasForeignKey(a => a.EstadoId);

Estadomap

HasRequired(p => p.CidadeLista).WithRequiredPrincipal().Map(p => p.MapKey("EstadoId"));

I switched to

HasRequired(a => a.Pais).WithMany(a => a.EstadoLista).HasForeignKey(a => a.PaisId);

Cidadeentity

I added

public int EstadoId { get; set; }

Estadoentity

I added

public int PaisId { get; set; }

My context was as follows

public class ExemploContext : DbContext
    {
        public ExemploContext()
            :base("DefaultConnection")
        {

        }

        public DbSet<EstadoEntity> Estados { get; set; }

        public DbSet<CidadeEntity> Cidades { get; set; }

        public DbSet<PaisEntity> Paises { get; set; }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Configurations.Add(new EstadoMap());
            modelBuilder.Configurations.Add(new CidadeMap());
            modelBuilder.Configurations.Add(new PaisMap());

            base.OnModelCreating(modelBuilder);
        }
    }

The source code of the example you can get here

I’m not very good with concepts, but in practice the example I gave is how I normally work with mapping relationships in Entityframework using Fluent API