EFListExtension.cs

    public static class DbContextExtensions
    {
        /// <summary>
        /// Add, update or delete a nested property list regardless of enabled auto changetracking
        /// </summary>
        /// <typeparam name="TSourceListEntry">Type of sourcelist like XXViewModel</typeparam>
        /// <typeparam name="TTargetListEntry">Type of targetlist like DbModel</typeparam>
        /// <typeparam name="TKey">Type of key</typeparam>
        /// <param name="context"></param>
        /// <param name="oldValues">List of dbmodels</param>
        /// <param name="newValues">List of dtoModels</param>
        /// <param name="sourceEqualProperty"></param>
        /// <param name="targetEqualProperty"></param>
        public static void AddOrUpdateOrDeleteList<TSourceListEntry, TTargetListEntry, TKey>(
            this DbContext context,
            ICollection<TTargetListEntry> oldValues,
            ICollection<TSourceListEntry> newValues,
            Func<TSourceListEntry, TKey> sourceEqualProperty,
            Func<TTargetListEntry, TKey> targetEqualProperty)
        {
            List<TTargetListEntry> newEntries = new List<TTargetListEntry>();
            ICollection<TTargetListEntry> targetList = oldValues;
            //Check for updates
            foreach (TTargetListEntry targetListEntry in targetList)
            {
                bool stillExists = false;
                foreach (TSourceListEntry sourceListEntry in newValues)
                {
                    if (targetEqualProperty(targetListEntry).Equals(sourceEqualProperty(sourceListEntry)))
                    {
                        //update
                        Mapper.Map(sourceListEntry, targetListEntry);
                        context.Entry(targetListEntry).State = EntityState.Modified;
                        stillExists = true;
                    }
                }

                if (!stillExists)
                {
                    context.Entry(targetListEntry).State = EntityState.Deleted;
                }
            }

            //Check for new entries
            foreach (TSourceListEntry newValue in newValues)
            {
                bool oldValueFound = false;
                foreach (TTargetListEntry oldValue in targetList)
                {
                    if (targetEqualProperty(oldValue).Equals(sourceEqualProperty(newValue)))
                    {
                        oldValueFound = true;
                        break;
                    }
                }

                if (!oldValueFound)
                {
                    newEntries.Add(Mapper.Map<TTargetListEntry>(newValue));
                }
            }


            foreach (TTargetListEntry targetListEntry in newEntries)
            {
                //add to target and update changetracking
                targetList.Add(targetListEntry);
                context.Entry(targetListEntry).State = EntityState.Added;
            }
        }
    }

Not tested, just straight outta ma head 💯