我必须以元组的格式返回结果，但是由于嵌套的foreach循环，我不能使用yield return（tuple）。我该怎么办？

public static IEnumerable<(string category, IEnumerable<Product> productsName)> GroupJoinQuery()
{
            string[] categories =
            {
                "Vegetables",
                "Dairy Products",
                "Seafood"
            };

            List<Product> products = Products.ProductList;

            var q = categories.GroupJoin(products, c => c, p => p.Category, (c, ps)
=> new { Category = c, Products = ps });

            foreach (var v in q)
            {
                Console.WriteLine($"{v.Category}:");
                foreach (var p in v.Products)
                {
                    Console.WriteLine($"   {p.ProductName}");
                }
            }
        }