CODEWITHSUNDEEP
c#entity-frameworkef-code-firstentity-framework-5
user1824269
user1824269

Reputation: 633

EF Delete Child Collection

I've the following:

class City {
    int id;
    string Name;
    ICollection<Person> Persons;
}

class Person {
   int id;
   string Name;
}

Which is the correct way to delete a City and all related Person? Possibly I'd like to avoid foreign key constraint and do it manually. I've tried:

public bool Delete(int id // City Id)
{
    City city = _db.Cities
                .Include(c => c.Persons)
                .First(c => c.Id == id);
    if(city != null)
    {
        foreach (Person person in city.Persons)
        {
            _db.Persons.Remove(person);
        }

        _db.Cities.Remove(city);

        _db.SaveChanges();
        return true;
    }

    return false;
}

But no person or city are being removed from the database.

Upvotes: 4

Views: 409

Answers (1)

kzfabi
kzfabi

Reputation: 2075

Your code seems correct...

You could also try using below code to delete entities:

foreach (Person person in city.Persons)
{
    _db.Persons.Entry(person).State = EntityState.Deleted;
}

_db.Cities.Entry(city).State = EntityState.Deleted;

_db.SaveChanges();

One more thing...

If you use First to get the City then the if statement will always be true since First expects to have a match and it throws an InvalidOperationException when the source sequence is empty.

Looking at your code I can see that the method returns true if there was a match by id and the deletion was performed, if there was no match it returns false. For city to be null you should use FirstOrDefault, it returns the default value of the type handled if the source sequence is empty, which in your case would be null.

Upvotes: 1

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