How to update child list in entity framework?

Question

These are models:

public class Contact
{
    public Contact() 
    {
        Emails = new List<Email>(); 
    }
    public int Id { get; set; }
    public string Name { get; set; }
    public string Surname { get; set; }
    public string Address { get; set; }
    public ICollection<Email> Emails { get; set; }

}
 public  class Email
{
    public int Id { get; set; }
    public string Name { get; set; }
    public virtual int ContactId { get; set; }
}

On my details page user is able to add more emails, delete exsting...etc...or change existing one. How to update collection? I tries this:

    var contactFromDb = db.Contacts.Include("Emails").Include("Telephones").Where(x => x.Id == contact.Id).FirstOrDefault();

      contactFromDb.Address = contact.Address;
      contactFromDb.Name = contact.Name;
      contactFromDb.Surname = contact.Surname;
      contactFromDb.Telephones = contact.Telephones;
      contactFromDb.Emails = contact.Emails;

String properties are updated nicely, I tried updating collection the same way, but I get duplicate values. How to update emails?

Answer 1

First delete removed emails:

var contactFromDb = db.Contacts.Include("Emails").Include("Telephones").FirstOrDefault(x => x.Id == updatedContact.Id);
contactFromDb.Address = updatedContact.Address;
contactFromDb.Name = updatedContact.Name;
contactFromDb.Surname = updatedContact.Surname;

// Delete removed emails
var emailsToDelete = (from email in contactFromDb.Emails
                        let item = updatedContact.Emails.SingleOrDefault(i => i.Id == email.Id)
                        where item == null
                        select email).ToList();
if (emailsToDelete.Any())
{
    foreach (var email in emailsToDelete)
    {
        db.Entry(email).State = EntityState.Deleted;
    }
}

After that update edited emails:

foreach (var email in updatedContact.Emails)
{
    // If id of an email is not equal to 0, it's not new email and it should be updated
    if (email.Id > 0)
    {
        var emailInDb = contactFromDb.Emails.Single(e => e.Id == email.Id);
        db.Entry(emailInDb).CurrentValues.SetValues(email);
        db.Entry(emailInDb).State = EntityState.Modified;
    }
}

And finally by calling db.SaveChanges() new emails with Id of 0 Will be inserted and you can repeat this cycle for Phones .

Answer 2

For child entites - easiest way is to delete them all and add new.

var contactFromDb = db.Contacts.Include("Emails").Include("Telephones").Where(x => x.Id == contact.Id).FirstOrDefault();

contactFromDb.Address = contact.Address;
contactFromDb.Name = contact.Name;
contactFromDb.Surname = contact.Surname;
contactFromDb.Telephones = contact.Telephones;
db.Entry(contactFromDb).State = System.Data.EntityState.Modified;
foreach(Email email in contactFromDb.Emails)
{
    db.Entry(email).State = System.Data.EntityState.Deleted;
}
contactFromDb.Emails.AddRange(contact.Emails);
db.SaveChanges();

Answer 3

Use this generic sub to mark the child state, easy to use

Notes:

• PromatCon: the entity object
• amList: is the child list that you want to add or modify
• rList: is the child list that you want to remove

updatechild(objCas.ECC_Decision, PromatCon.ECC_Decision.Where(c => c.rid == objCas.rid & !objCas.ECC_Decision.Select(x => x.dcid).Contains(c.dcid)).toList())

public void updatechild<Ety>(ICollection<Ety> amList, ICollection<Ety> rList)
{
    if (amList != null)
    {
        foreach (var obj in amList)
        {
            var x = PromatCon.Entry(obj).GetDatabaseValues();
            if (x == null)
                PromatCon.Entry(obj).State = EntityState.Added;
            else
                PromatCon.Entry(obj).State = EntityState.Modified;
        }
    }

    if (rList != null)
    {
        foreach (var obj in rList.ToList())
            PromatCon.Entry(obj).State = EntityState.Deleted;
    }
}

PromatCon.SaveChanges()