SyncUtil

private void sync<TEntity, TKey>(TEntity[] items, Func<TEntity, TKey> getId, TKey[] currentItemIds, out TKey[] keysToDelete, Action<TEntity> onAdd = null, Action<TEntity> onUpdate = null) where TEntity : class
{
    foreach (var item in items)
    {
        if (currentItemIds.Contains(getId(item)))
        {
            _context.Entry(item).State = EntityState.Modified;
            onUpdate?.Invoke(item);
        }
        else
        {
            _context.Entry(item).State = EntityState.Added;
            onAdd?.Invoke(item);
        }
    }
    keysToDelete = currentItemIds.Except(items.Select(i => getId(i))).ToArray();
}
private void sync_doDeletes<TEntity, TKey>(TKey[] keysToDelete, Action<TEntity> onDelete = null) where TEntity : class
{
    foreach (var currentItemId in keysToDelete)
    {
        var item = _context.Set<TEntity>().Find(currentItemId);
        //_context.Entry(item).State = EntityState.Deleted;
        _context.Remove(item);
        onDelete?.Invoke(item);
    }
}