How to Update Entity by Replacing in EF?

Question

I have a class Order which has a List<Item> and a Customer. I need to update Order and its child class. First I only attach the Order object but in this way EF cannot Understand changes in Items and Customers.

Then I tried changing the state of the child classes to EntityState.Modified but that didn't work either.Is there a way in EF to replac parent and child classes with existing record in db?

And if there isn't, how can I solve this problem?

var temp = db.Orders.Find(order.Id);
temp = order;
temp.Items = order.Items;
temp.Customer = order.Customer; 
db.SaveChanges(); 

i try this too after changing Order in user actions:

db.Orders.Attach(order) ;
db.SaveChanges();

Answer 1

I haven't tried this for Entities with Child classes but you could try setting the value.

context.Entry(temp).CurrentValues.SetValues(order);
context.SaveChanges();

This assumes that order is an instance of the Entity Orders. Note this will completely overwrite every property of the temp record with that of order.

This blog has more information (Also applies to EF Core): https://web.archive.org/web/20191225092110/http://kerryritter.com/updating-or-replacing-entities-in-entity-framework-6/

Answer 2

If you want to replace entity with related/child/nested references and collections you can use Tracked Graph since EF Core 2.2. All entities IDs should be database generated.

Add method to your context

public void Replace<TEntity>(TEntity oldEntity, TEntity newEntity) where TEntity : class
{
    ChangeTracker.TrackGraph(oldEntity, e => e.Entry.State = EntityState.Deleted);
    ChangeTracker.TrackGraph(newEntity, e => e.Entry.State = e.Entry.IsKeySet ? EntityState.Modified : EntityState.Added);
}

Usage

var oldOrder = db.Orders
        .AsNoTracking()
        .Include(o => o.Items)
        .Include(o => o.Customer)
        .Find(newOrder.Id);

db.Replace(oldOrder, newOrder);

db.SaveChanges();

Note that old entity should be detatched using AsNoTracking or

db.Entry(oldOrder).State = EntityState.Detached;