Entity Framework Code First - Invalid column name Discriminator

Question

Two Classes in codefirst

public partial class BaseEntity 
{
    public int ID { get; set; }
}

public partial class Fund : BaseEntity
{
   public int Name { get; set; }
}
public partial class InvestorFund : BaseEntity 
{
  public int FundID { get; set; }
}

Mapping Classes

this.Property(t => t.ID).HasColumnName("FundID");

My Code First Join SQL Query

from fund in context.Funds

join investorFund in context.InvestorFunds on fund.ID equals investorFund.FundID

Throws an Invalid column name Discriminator

Answer 1

You need to tell Code First how these classes relate to tables. There are three options:

• Table per type (TPT) would mean the fields defined on Fund and InvestorFund would go into their own tables and properties defined on BaseEntity would go to a table named BaseEntity. Querying would be slower as each entity now has to combine the fields from multiple tables.

  modelBuilder.Entity<Fund>().ToTable("Funds");
  modelBuilder.Entity<InvestorFund>().ToTable("InvestorFunds");
  

• Table per heirarchy (TPH) would mean that Fund, InvestorFund and BaseEntity properties would all be merged into a single table named BaseEntity and an extra field would be required to indicate which row is which type. This extra field is called the discriminator.

  modelBuilder.Entity<BaseEntity>()
    .Map<Fund>(m => m.Requires("Discriminator").HasValue("F"))
    .Map<InvestorFund>(m => m.Requires("Discriminator").HasValue("I"));
  

• Table per concrete type (TPC) would mean that Fund and InvestorFund each have their own table which would also include any fields needed for their base classes.

  modelBuilder.Entity<Fund>().Map(m => {
                m.MapInheritedProperties();
                m.ToTable("Funds"); 
  }); 
  modelBuilder.Entity<InvestorFund>().Map(m => {
                m.MapInheritedProperties();
                m.ToTable("InvestorFunds"); 
  });