Saving in entity framework
Solution 1
You ask:
Don't we need call _context.SaveChanges() in every Delete/Update/... operations?
No we don't. When calling Delete
we don't accually delete the entity - we mark it for deletion.
Same thing with Update
, although you dont have to do anything other that make the changes you want to the entity. All properties (generated by the default template) will implement INotifyPropertyChanged
so it knows when a entity is modified.
All entities (in database first - autogenerated by defullt template) have a State
property. This property is maintained by the ObjectContext
as long as the chages take place within the scope of the ObjectEntity.
e.g.
Customer c;
using(var context = new MyEntityContext())
{
c = context.Customer.FirstOrDefault(); //state is now Unchanged
c.Name = "new name"; // this set the State to Modified
//context.SaveChanges(); // will persist the data to the store, and set the State back to unchaged
}
//if we look at our customer outside the scope of our context
//it's State will be Detacth
Console.WriteLine(c.State);
Then you call SaveChanges
all entites that have a state of Added
Deleted
or Modified
will have their changes persisted to the database in a local transaction
EDIT
If an entity is marked for deletion, and you try to modify it - you will get an InvalidOperationException
Solution 2
You can perform many changes in your in-memory context, such as inserts, updates and deletes. Once you call SaveCahnges() all the changes you've made will be saved in the DB at a single transaction. This means that eiteher they are all submited, or none of them in case of an error.
NET
Updated on July 26, 2022Comments
-
NET almost 2 years
I have read this article and still misunderstanding key moments. Don't we need call
_context.SaveChanges()
in every Delete/Update/... operations?
If I change property of any entity does
SaveChanges()
submitted result to database or I must manually setEntityState.Modifyed
?Here is my code:
public class Repository<T> : IRepository<T> where T : class { private IDbContext _context; public Repository(IDbContext context) { _context = context; } private IDbSet<T> DbSet { get { return _context.Set<T>(); } } #region IRepository<T> Members public void Insert(T entity) { DbSet.Add(entity); } public void Delete(T entity) { DbSet.Remove(entity); } public IQueryable<T> SearchFor(Expression<Func<T, bool>> predicate) { return DbSet.Where(predicate); } public IQueryable<T> GetAll() { return DbSet; } public T GetById(int id) { return DbSet.Find(id); } #endregion } public interface IDbContext { IDbSet<T> Set<T>() where T : class; int SaveChanges(); void Dispose(); }
-
NET about 11 yearsso must I implement SaveChanges method in IRepository ?
-
omer schleifer about 11 yearsI'm not sure why you would want to wrap the context with your repository class. you can work with the context directly. e.g. context.Cars.AddObject(new Car()) , etc...
-
NET about 11 yearsso i need call Repository.GetAll().SaveChanges() to submit changes.Does I can still query deleted items (marked as deleted)?
-
Jens Kloster about 11 yearsyes you need to be able to call
Savechanges
. Definitely. I think you could still query an item that is marked for deletion, although i would not advice it - I don't think an entity can go fromDeleted
toModified
-
Jens Kloster about 11 yearsI updated my answer. You get an exception if you try to modify an entity that is marked for deletion.