c# - DbSet.Add & DbSet.Remove Versus using EntityState.Added & EntityState.Deleted -

in entity framework 6 there multiple way of adding / removing entities, example adding entities, can use:-

b.students.add(student); db.savechanges(); 

or

db.entry(student).state = entitystate.added; db.savechanges(); 

and when deleting object:-

db.entry(studenttodelete).state = entitystate.deleted; db.savechanges(); 

or

db.remove(studenttodelete) db.savechanges(); 

i did not find resources talks differences , , of online tutorials mention both approaches if same. have read reply on article link using dbset.add set status entity , related entities/collections added, while using entitystate.added adds related entities/collections context leaves them unmodified, , same thing applies dbset.remove & entitystate.deleted

so these differences correct ?

edit

as understand graph operation means both parent , child got deleted/added , if parent marked deletion or addition. did these 2 tests :-

using (var db = new testcontext()) {     var = new department { departmentname = "shipping" };     var b = new employee { firstname = "bob", lastname = "dodds", department = };     db.entry(b).state = entitystate.added;     db.savechanges(); }    using (var db = new testcontext()) {     var a2 = new department { departmentname = "production" };     var b2 = new employee { firstname = "sarah", lastname = "gomez", department = a2 };     db.employees.add(b2);     db.savechanges(); } 

where both have added dept & employee. can adivce on please?

from lerman & miller's dbcontext book (p. 80):

calling dbset.add , setting state added both achieve same thing.

which is:

if entity not tracked context, start being tracked context in added state. both dbset.add , setting state added graph operations— meaning other entities not being tracked context , reachable root entity marked added. if entity (the root entity - addiditon) tracked context, moved added state.

note incorrectly answered in question refer to. book written ef 4.3 in mind, , doesn't mention breaking change since ef 4.1 when dbcontext introduced.

setting entity's state deleted (either through dbset.remove() or setting entry(entity).state deleted) not graph operation. affects entity's state, not entities in object graph.

the latter true entity state except added.

an exception rule when cascaded delete configured, both in database , in ef model. in many-to-many association hidden junction table, cascaded delete default, junction records deleted when root entity marked delete (either setting state deleted or removing dbset).

for instance, let a , b have many-to-many association. junction table ab in database, not in class model. if fetch a database (without include()-ing bs) , delete it, a deleted , al of ab records, no bs deleted.

when in one-to-many association cascaded delete configured 'many' entities deleted when '1' entity deleted. if a , b have one-to-many association, deleting a delete bs.