Entity Framework ModelBuilder in two different files?

Question

Is it possible to have ModelBuilders for Entities to be in different files? We are trying to separate automatic scaffolding from database, and have certain manual customization also.

This is what I am attempting, receiving error below,

File 1:

modelBuilder.Entity<PropertyMailingAddress>(entity =>
{
    entity.HasOne(d => d.LkAddressType)
        .WithMany(p => p.PropertyMailingAddress)
        .HasForeignKey(d => d.LkAddressTypeId)
        .HasConstraintName("FK_PropertyMailingAddress_LK_AddressTypeId");

File 2:

modelBuilder.Entity<PropertyMailingAddress>(entity =>
{

    entity.HasOne(d => d.LkSourceOfAddress)
        .WithMany(p => p.PropertyMailingAddress)
        .HasForeignKey(d => d.LkSourceOfAddressId)
        .HasConstraintName("FK_PropertyMailingAddress_LK_SourceOfAddressId");

Error CS1501 No overload for method 'Entity' takes 2 arguments

Is it possible to have partial class methodology for this?

hi @bolkay can you provide in code example, and I can send points? not sure how to implement extension method for this question topic thanks — , May 06 '20 at 20:39

Francesc Castells · Accepted Answer · 2020-05-06T21:01:59.443

If you want to have a file per Entity then, instead of using the Model Builder, use the IEntityTypeConfiguration. Create a class implementing IEntityTypeConfiguration<T> per entity. For example:

public class PropertyMailingAddressConfig : IEntityTypeConfiguration<PropertyMailingAddress>
{
  public void Configure(EntityTypeBuilder<PropertyMailingAddress> builder)
  {
     builder
       .HasOne(d => d.LkAddressType);
       .WithMany(p => p.PropertyMailingAddress);
       .HasForeignKey(d => d.LkAddressTypeId)
       .HasConstraintName("FK_PropertyMailingAddress_LK_AddressTypeId");
  }
}

The default conventions apply the same way, so a property called Id will automatically be mapped as Primary Key and so on.

You then need to tell Entity Framework to load the entity configurations from the files found in a given Assembly:

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder
      .ApplyConfigurationsFromAssembly(Assembly.GetExecutingAssembly()); 
}

score 1 · Answer 2 · answered May 07 '20 at 08:29

You can do this by setting the dbcontext class to partial, creating the partial class in two files, and then defining a method in one of the files to pass the ModelBuilder parameters.

For details, please refer to the following.

File1:

  public partial class MyDbContext: DbContext
    {
        public DbContext(DbContextOptions<MyDbContext> options)
            : base(options)
        {
        }
        public DbSet<PropertyMailingAddress> PropertyMailingAddress{ get; set; } 

        partial void OnModelCreatingPartial(ModelBuilder modelBuilder);

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            OnModelCreatingPartial(modelBuilder);

            modelBuilder.Entity<PropertyMailingAddress>(entity =>
            {
              entity.HasOne(d => d.LkAddressType)
                    .WithMany(p => p.PropertyMailingAddress)
                    .HasForeignKey(d => d.LkAddressTypeId)
                    .HasConstraintName("FK_PropertyMailingAddress_LK_AddressTypeId");
            });  
        }
    }

File2:

     public partial class MyDbContext : DbContext
        {
            partial void OnModelCreatingPartial(ModelBuilder modelBuilder)
            {
               modelBuilder.Entity<PropertyMailingAddress>(entity =>
               {    

                  entity.HasOne(d => d.LkSourceOfAddress)
                        .WithMany(p => p.PropertyMailingAddress)
                        .HasForeignKey(d => d.LkSourceOfAddressId)

 .HasConstraintName("FK_PropertyMailingAddress_LK_SourceOfAddressId");
               });
            }           
        }

You can refer to this.

score 0 · Answer 3 · answered May 06 '20 at 20:45

I really don't know why you want to have separate configuration file for a single entity. However, based on what you have provided, you can do this:

public partial static class MyExtensions
{
 public static void ConfigureMyEntity(this ModelBuilder modelBuilder)
{
modelBuilder.Entity<MyEntity>()
.HasOne<Other>()
.WithMany()
....
}
}

If you want to define configurations for separate entities, there are cleaner ways to do that.

Entity Framework ModelBuilder in two different files?

3 Answers3