Question

Entity Framework Code First:

Suppose I want to create table relationships, where is the good place to put code in?

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<table1>().HasMany(i => i.AllowedDestinations).WithMany(d => d.something)
      ......

Or other place other than OnModelCreating?

Answer 1

You can create a class called “MYEntityConfiguration” (where MyEntity is the type of entity you are trying to configure) and inherit from the EntityTypeConfiguration<> type found in Entity Framework.

For example….

public class Position
    {
        public int Id { get; set; }

        public string CompanyName { get; set; }

        public bool IsCurrentRole { get; set; }

        public string Summary { get; set; }

        public string Title { get; set; }

        public int? StartMonth { get; set; }

        public int? StartYear { get; set; }

        public int? EndMonth { get; set; }

        public int? EndYear { get; set; }

        public virtual User User { get; set; }
        public int UserId { get; set; }
    }

and the corresponding configuration file….

public class PositionConfiguration : EntityTypeConfiguration<Position>
{
    public PositionConfiguration()
    {
        this.ToTable("Positions");
        this.HasKey(p => p.Id);
        this.Property(p => p.Id).HasColumnName("PositionId").HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);

        this.Property(p => p.CompanyName).HasColumnName("CompanyName");
        this.Property(p => p.EndMonth).IsOptional().HasColumnName("EndMonth");
        this.Property(p => p.EndYear).IsOptional().HasColumnName("EndYear");
        this.Property(p => p.IsCurrentRole).IsOptional().HasColumnName("IsCurrentRole");
        this.Property(p => p.StartMonth).IsOptional().HasColumnName("StartMonth");
        this.Property(p => p.StartYear).IsOptional().HasColumnName("StartYear");

        this.Property(p => p.Summary).HasColumnName("Summary");
        this.Property(p => p.Title).HasColumnName("Title");
    }
}

Then in your DBContext… OnModelCreating…

protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Configurations.Add(new PositionConfiguration());

            base.OnModelCreating(modelBuilder);
        }

That will keep your configurations nice and contained… I found it to be the best way.