Entity splitting with optional relation - (EF code first) - entity-framework

Question

I have 2 tables: an Orders table and an OrderActivity table. If no activity has been taken on an order, there will be no record in the OrderActivity table. I currently have the OrderActivity table mapped as an optional nav property on the Order entity and I handle updates to OrderActivity like this:
if (order.OrderActivity == null)
{
order.OrderActivity = new OrderActivity();
}
order.OrderActivity.LastAccessDateTime = DateTime.Now;
Is it possible to consolidate this such that the columns of the OrderActivity table are mapped to properties on the Orders entity, and will default if there is no OrderActivity record? Configuration for entity splitting only appears to work if records exist in both tables. If it is not possible, what is the best practice to obscure the child entity from my domain model? My goal is to keep the model as clean as possible while interacting with a DB schema that I have no control over.

Answer 1

You can create the mapping and specify the type of LastAccessDate as Nullable<DateTime>. The mapping will create one-to-one with LastAccessDate being optional.
public class Order {
[Key]
public int Id { get; set; }
public string Name { get; set; }
public DateTime? LastAccessDate { get; set; }
}
modelBuilder.Entity<Order>().Map(m => {
m.Properties(a => new { a.Id, a.Name });
m.ToTable("Order");
}).Map(m => {
m.Properties(b => new { b.Id, b.LastAccessDate });
m.ToTable("OrderActivity");
});
In this case, specifying LastAccessDate property is optional when inserting new orders.
var order = new Order();
order.Name = "OrderWithActivity";
order.LastAccessDate = DateTime.Now;
db.Orders.Add(order);
db.SaveChanges();
order = new Order();
order.Name = "OrderWithoutActivity";
db.Orders.Add(order);
db.SaveChanges();
Note this will always create one entry in each table. This is necessary because EF creates INNER JOIN when you retrieve Orders and you want to get all orders in this case. LastAccessDate will either have a value or be null.
// Gets both orders
var order = db.Orders.ToList();
// Gets only the one with activity
var orders = db.Orders.Where(o => o.LastAccessDate != null);