Retrieving entity from context after Add() yet before SaveChanges() has been called

Question

Let's assume I have a file with multiple rows each representing a Person, the Person entity has an identity column that is also the primary key. Assuming that a Person can be repeated in the file, if it is, perhaps I want to do a last entry wins scenario. In the example below I use a repository to retrieve a person from the database by the social security number. The issue is that when the same SSN shows up again in the file, the repository still returns a null, even though technically that person with that SSN has already been added to the context (SaveChanges hasn't been called yet). I realize I can work around this by tracking myself which Person objects have already been added. I am wondering what is the best practice for this scenario. Thanks.

foreach(row in fileRows)
{
    Person person = personRepository.GetBySSN(row.SSN);

    if(person == null)
    {
        //insert logic
    }
    else
    {
        //update logic
    }
}

personRepository.SaveChanges();

Answer 1

I think I can give the same answer I gave here

To persist an entity you usually add it to it's DbSet in the context.

For example

var bar = new Bar();
bar.Name = "foo";
var context = new Context();
context.Bars.Add(bar);

Surprisingly, querying context.Bars, the just added entity cannot be found

var howMany = context.Bars.Count(b => b.Name == "foo");
// howMany == 0

After context.SaveChanges() the same line will result 1

The DbSet seems unaware to changes until they're persisted on db.

Fortunately, each DbSet has a Local property that acts like the DbSet itself, but it reflect all in-memory operations

var howMany = context.Bars.Local.Count(b => b.Name == "foo");
// howMany == 1

You can also use Local to add entities

context.Bars.Local.Add(bar);

and get rid of the weird behavior of Entity Framework.