Question

Entities

public abstract class Person
{
  public string FirstName { get; set; }
  public string LastName { get; set; }
  public string WorkPhone { get; set; }
  public string Discriminator { get; set; }
}

public class Friend : Person
{
  public string HomePhone { get; set; }
}

public class Family : Person
{
  public string CellPhone { get; set; }
}

public class Colleague : Person
{
  // No home phone
}

Mappings

public class PersonMap : EntityTypeConfiguration<Person>
{
  public PersonMap()
  {
    Property(t => t.FirstName).HasColumnName("First_Name");
    Property(t => t.LastName).HasColumnName("Last_Name");
    Property(t => t.WorkPhone).HasColumnName("Work_Phone");

    Map<Friend>(m => m.Requires("Discriminator").HasValue("Friend");
    Map<Family>(m => m.Requires("Discriminator").HasValue("Family");
    Map<Colleague>(m => m.Requires("Discriminator").HasValue("Colleague");
  }
}

public class FriendMap : EntityTypeConfiguration<Friend>
{
  public FriendMap()
  {
    Property(t => t.HomePhone).HasColumnName("Home_Phone");
  }
}

public class FamilyMap : EntityTypeConfiguration<Family>
{
  public FamilyMap()
  {
    Property(t => t.CellPhone).HasColumnName("Home_Phone");
  }
}

Note: ColleagueMap has no mapping for "Home_Phone"

DbContext

public override void OnModelCreating(DbModelBuilder modelBuilder)
{
  ...
  modelBuilder.Configurations.Add(new PersonMap());
  modelBuilder.Configurations.Add(new FriendMap());
  modelBuilder.Configurations.Add(new FamilyMap());
  ...
}

Entity Framework is telling me that I cannot map two properties to the same column:

System.Data.MetadataException: Schema specified is not valid. Errors:
Each property name in a type must be unique. Property name
‘Home_Phone’ was already defined.

I can’t find any examples of TPH inheritance where multiple subclasses map different properties to the same columns. Is this possible in EF?

Answer 1

Short answer is no. Each property must have its own column. It is not possible to map multiple properties in inheritance hierarchy to the same column.