Question

virI’m trying to create a lookup table in my ASP.NET MVC4 application with Entity Framework Code First. It is for our locations and there should be two entries. I need to have some sort of ID associated with them so there is a LocationID stored in my Software table. However, when I create them there is an entry to created for each row in the Software Table.

Here is my Software class:

public class Software
    {
        public int Id { get; set; }
        public virtual List<SoftwareType> SoftwareTypes { get; set; }
        public virtual List<Location> Locations { get; set; }
        public virtual List<SoftwarePublisher> Publishers { get; set; }
        [Required]
        [StringLength(128)]
        public string Title { get; set; }
        [Required]
        [StringLength(10)]
        public string Version { get; set; }
        [Required]
        [StringLength(128)]
        public string SerialNumber { get; set; }
        [Required]
        [StringLength(3)]
        public string Platform { get; set; }
        [StringLength(1000)]
        public string Notes { get; set; }
        [Required]
        [StringLength(15)]
        public string PurchaseDate { get; set; }
        public bool Suite { get; set; }
        public string SubscriptionEndDate { get; set; }
        //[Required]
        //[StringLength(3)]
        public int SeatCount { get; set; }

    }

Here is my Locations class:

 public class Location
    {
        public int Id { get; set; }
        [Required]
        [StringLength(20)]
        public string LocationName { get; set; }
        public virtual Software Software { get; set; }
    }

Here is my Global.asax call to a seed method:

Database.SetInitializer(new SampleData());
            using (var context = new Context())
            {
               context.Database.Initialize(true);
            }

Here is my context:

 public class Context : DbContext
    {
        public DbSet<Software> Software { get; set; }
        public DbSet<Location> Locations { get; set; }
        public DbSet<SoftwarePublisher> SoftwarePublishers { get; set; }
        public DbSet<SoftwareType> SoftwareTypes { get; set; }

        public Context()
        {
           Configuration.ProxyCreationEnabled = false;
        }
    }

And here is my seeding:

public class SampleData : CreateDatabaseIfNotExists<Context>
    {
        protected override void Seed(Context context)
        {
            new List<Software> {
                    new Software { 
                         Title = "Adobe Creative Suite", 
                         Version = "CS6", 
                         SerialNumber = "1234634543", 
                         Platform = "Mac", 
                         Notes = "Macs rock!", 
                         PurchaseDate = "2012-12-04", 
                         Suite = true, 
                         SubscriptionEndDate = null, 
                         SeatCount = 0, 
                         SoftwareTypes = new List<SoftwareType> 
                               { new SoftwareType { Type="Suite" }}, 
                         Locations = new List<Location> 
                               { new Location { LocationName = "Paradise" }},
                         Publishers = new List<SoftwarePublisher> 
                               { new SoftwarePublisher { Publisher = "Adobe" }}},
                ...other similar rows...
                }.ForEach(s => context.Software.Add(s));

            base.Seed(context);
            context.SaveChanges(); 

        }

Because I am creating a new list for things like Locations (I need to fix the other things like SoftwareType and Publisher, but let’s focus on Locations), it is creating a new row in my Locations table. How do I restructure my classes, so that I have two entries in my Locations table and then IDs in my Software table pointing to one of those two entries? Please bear in mind I am an Entity Framework newbie, so please try to be explicit. Thanks.

Answer 1

I think you want a many to many relationship between Software and Locations. To do that, you’ll need to create a join table (also called a linking table). I believe you want to do this in your OnModelCreating override

this.HasMany(i => i.Softwares)
            .WithMany(c => c.Locations)
            .Map(mc =>
            {
                mc.MapLeftKey("SoftwareId");
                mc.MapRightKey("LocationId");
                mc.ToTable("SoftwareLocations");
            });

I got that snippet from this blog post