EF 之 context.Savechanges()

EF查出來了List,然後循環改變這裏面的值，可以批量修改嗎？

測試，是可以的。

看看 context.Savechanges() 發生了什麼。

  public virtual int SaveChanges(bool acceptAllChangesOnSuccess)
        {
            CheckDisposed();

            DbContextDependencies.UpdateLogger.SaveChangesStarting(this);

            TryDetectChanges();

            try
            {
                var entitiesSaved = DbContextDependencies.StateManager.SaveChanges(acceptAllChangesOnSuccess);

                DbContextDependencies.UpdateLogger.SaveChangesCompleted(this, entitiesSaved);

                return entitiesSaved;
            }
            catch (DbUpdateConcurrencyException exception)
            {
                DbContextDependencies.UpdateLogger.OptimisticConcurrencyException(this, exception);

                throw;
            }
            catch (Exception exception)
            {
                DbContextDependencies.UpdateLogger.SaveChangesFailed(this, exception);

                throw;
            }
        }

TryDetectChanges 這個方法下去是

    /// <summary>
        ///     This API supports the Entity Framework Core infrastructure and is not intended to be used
        ///     directly from your code. This API may change or be removed in future releases.
        /// </summary>
        public virtual void DetectChanges(IStateManager stateManager)
        {
            _logger.DetectChangesStarting(stateManager.Context);

            foreach (var entry in stateManager.ToList()) // Might be too big, but usually _all_ entities are using Snapshot tracking

            {
                if (entry.EntityType.GetChangeTrackingStrategy() == ChangeTrackingStrategy.Snapshot
                    && entry.EntityState != EntityState.Detached)
                {
                    LocalDetectChanges(entry);
                }
            }

            _logger.DetectChangesCompleted(stateManager.Context);
        }

這裏會把所有entry.EntityState != EntityState.Detached 這個狀態的實體收集起來。

/// <summary>
        ///     This API supports the Entity Framework Core infrastructure and is not intended to be used
        ///     directly from your code. This API may change or be removed in future releases.
        /// </summary>
        public virtual void AddToCollectionSnapshot([NotNull] IPropertyBase propertyBase, [NotNull] object addedEntity)
        {
            EnsureRelationshipSnapshot();
            _relationshipsSnapshot.AddToCollection(propertyBase, addedEntity);
        }

detect之後，在改變他們