Entity Framework Core: How do I update a record with nested fields? - entity-framework

Question

I've got a simple "ContactsList" ASP.Net Core Web (REST) application, .Net Core 3.0, an MSSQL LocalDB, using MSVS 2019.
My "Contact" entity contains a list of "Notes".
When I create a new contact that already contains one or more notes, everything works fine. EF automagically inserts the notes into the notes table.
But when I try to UPDATE a contact, EF seems to disregard "notes".
Q: For "Updates", do I need write code in my controller to explicitly update the notes myself?
Or am I doing something "wrong", such that EF can't "automagically" do the updates it's supposed to?
Models/Contact.cs:
public class Contact
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int ContactId { get; set; }
public string Name { get; set; }
public string EMail { get; set; }
public string Phone1 { get; set; }
public string Phone2 { get; set; }
public string Address1 { get; set; }
public string Address2 { get; set; }
public string City { get; set; }
public string State { get; set; }
public string Zip { get; set; }
public List<Note> Notes { get; set; }
}
Models/Note.cs:
public class Note
{
public Note()
{
this.Date = DateTime.Now; // Default value: local "now"
}
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int NoteId { get; set; }
public string Text { get; set; }
public DateTime Date { get; set; }
[ForeignKey("Contact")]
public int ContactId { get; set; }
}
Controllers/ContactsController.cs (POST works: if there are notes in the contacts list, it adds them):
[HttpPost]
public async Task<ActionResult<Contact>> PostContact(Contact contact)
{
_context.Contacts.Add(contact);
await _context.SaveChangesAsync();
//return CreatedAtAction("GetContact", new { id = contact.ContactId }, contact);
return CreatedAtAction(nameof(GetContact), new { id = contact.ContactId }, contact);
}
Controllers/ContactsController.cs (PUT seems to completely disregard any assocated notes):
[HttpPut("{id}")]
public async Task<IActionResult> PutContact(int id, Contact contact)
{
if (id != contact.ContactId)
{
return BadRequest();
}
_context.Entry(contact).State = EntityState.Modified;
try
{
await _context.SaveChangesAsync();
}
catch (DbUpdateConcurrencyException)
{
if (!ContactExists(id))
{
return NotFound();
}
else
{
throw;
}
}
return NoContent();
}
The SQL for POST shows four separate INSERTs: one for the contact, and one for each note.
The SQL for PUT only shows one UPDATE: just the contact; nothing else.
The debugger shows "notes" are clearly part of the "Contact" record that the controller received by PutContact().
Q: Should EF deal with "updating" notes automagically, or do I need to hand-code my updates in the controller?

Answer 1

Entity Framework Core ignores relationships unless you explicitly include them in queries.
_context.Entry(contact).State = EntityState.Modified;
The problem with the line above is that you did not specify that the related data has been modified, so it will be ignored in the query.
So you can either
attach all the related data
set the state of the related data to EntityState.Modified
or you can
query the object in the database and include the related data
and then assign the contact object to that queried object
var dbContactObj = _context.Contacts.Include(x => x.Notes).First(x => x.Id == contact.Id);
dbContactObj = contact;
_context.SaveChangesAsync();