Entity framework replaces delete+insert with an update. How to turn it off - entity-framework

Question

I want to remove a row in database and insert it again with the same Id, It sounds ridiculous, but here is the scenario:
The domain classes are as follows:
public class SomeClass
{
public int SomeClassId { get; set; }
public string Name { get; set; }
public virtual Behavior Behavior { get; set; }
}
public abstract class Behavior
{
public int BehaviorId { get; set; }
}
public class BehaviorA : Behavior
{
public string BehaviorASpecific { get; set; }
}
public class BehaviorB : Behavior
{
public string BehaviorBSpecific { get; set; }
}
The entity context is
public class TestContext : DbContext
{
public DbSet<SomeClass> SomeClasses { get; set; }
public DbSet<Behavior> Behaviors { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>();
modelBuilder.Entity<SomeClass>()
.HasOptional(s => s.Behavior)
.WithRequired()
.WillCascadeOnDelete(true);
}
}
Now this code can be executed to demonstrate the point
(described with comments in the code below)
using(TestContext db = new TestContext())
{
var someClass = new SomeClass() { Name = "A" };
someClass.Behavior = new BehaviorA() { BehaviorASpecific = "Behavior A" };
db.SomeClasses.Add(someClass);
// Here I have two classes with the state of added which make sense
var modifiedEntities = db.ChangeTracker.Entries()
.Where(entity => entity.State != System.Data.Entity.EntityState.Unchanged).ToList();
// They save with no problem
db.SaveChanges();
// Now I want to change the behavior and it causes entity to try to remove the behavior and add it again
someClass.Behavior = new BehaviorB() { BehaviorBSpecific = "Behavior B" };
// Here it can be seen that we have a behavior A with the state of deleted and
// behavior B with the state of added
modifiedEntities = db.ChangeTracker.Entries()
.Where(entity => entity.State != System.Data.Entity.EntityState.Unchanged).ToList();
// But in reality when entity sends the query to the database it replaces the
// remove and insert with an update query (this can be seen in the SQL Profiler)
// which causes the discrimenator to remain the same where it should change.
db.SaveChanges();
}
How to change this entity behavior so that delete and insert happens instead of the update?

Answer 1

A possible solution is to make the changes in 2 different steps: before someClass.Behavior = new BehaviorB() { BehaviorBSpecific = "Behavior B" }; insert
someClass.Behaviour = null;
db.SaveChanges();
The behaviour is related to the database model. BehaviourA and B in EF are related to the same EntityRecordInfo and has the same EntitySet (Behaviors).
You have the same behaviour also if you create 2 different DbSets on the context because the DB model remains the same.
EDIT
Another way to achieve a similar result of 1-1 relationship is using ComplexType. They works also with inheritance.
Here an example
public class TestContext : DbContext
{
public TestContext(DbConnection connection) : base(connection, true) { }
public DbSet<Friend> Friends { get; set; }
public DbSet<LessThanFriend> LessThanFriends { get; set; }
}
public class Friend
{
public Friend()
{Address = new FullAddress();}
public int Id { get; set; }
public string Name { get; set; }
public FullAddress Address { get; set; }
}
public class LessThanFriend
{
public LessThanFriend()
{Address = new CityAddress();}
public int Id { get; set; }
public string Name { get; set; }
public CityAddress Address { get; set; }
}
[ComplexType]
public class CityAddress
{
public string Cap { get; set; }
public string City { get; set; }
}
[ComplexType]
public class FullAddress : CityAddress
{
public string Street { get; set; }
}