var qry = _productRepository.Table.GroupJoin(_categoriesRepository.Table,
            p => p.CategoryId,
            c => c.Id,
            (p, c) => new { Product = p, Categories = c.DefaultIfEmpty() })
            .Where(hdg => hdg.Product.Hidden == false)

            .SelectMany(final => final.Categories,
            (final, c) => new CatalogItemResponse
            {
                ChildrenCategoryId = final.Product.ChildrenCategoryId,
                //DistributionCenterErpId = final.Product.DistributionCenterErpId,
                //Atribuições
                .......
             }).ToList();

qry.ForEach(q =>
            {
                var product = new Product();

                product.CategoryId = q.CategoryId;
                product.AuthorizeMaximumPercentageAlteration = q.AuthorizeMaximumPercentageAlteration;
                product.AuthorizeMinimumPercentageAlteration = q.AuthorizeMinimumPercentageAlteration;
                product.HaveMaximumPercentage = q.HaveMaximumPercentage;
                product.HaveMinimumPercentage = q.HaveMinimumPercentage;
                product.Hidden = q.Hidden;
                product.ChildrenCategoryId = q.ChildrenCategoryId;
                product.Description = q.Description;
                //product.DistributionCenterErpId = q.DistributionCenterErpId;
                //Mais atribuições e etc
});