Linq group join

Question

How to write Description from Recipe in recipe=. I tried to use join r in Recipe on d.DishID equals r.DishID but it giving wrong result. It erase one item in result1.

Exptected output:

namespace ConsoleApplication3
{
    class Program
    {
        static void Main(string[] args)
        {
            List<Component> Component = new List<Component>();
            List<Dish> Dish = new List<Dish>();
            List<Recipe> Recipe = new List<Recipe>();
            Dish.Add(new Dish { DishID = 9, CategoryID = 6, DishName = "Pork" });
            Dish.Add(new Dish { DishID = 10, CategoryID = 6, DishName = "Beef" });
            Component.Add(new Component { ComponentID = 1, DishID = 9, AmountID = "1", NameID = "1" });
            Recipe.Add(new Recipe { DishID = 9, RecipeID = 0, Description = "Test" });

            var result1 = (
            from d in Dish
            //join r in Recipe on d.DishID equals r.DishID 
            join c in Component on d.DishID equals c.DishID into items
            select new Item { DishID = d.DishID, components = items.ToList() recipe=}
            ).ToList();
        }
    }
    public class Item
    {
        public int DishID { get; set; }

        public string DishName { get; set; }

        public string recipe { get; set; }

        public List<Component> components { get; set; }
    }

    public partial class Component
    {
        public int ComponentID { get; set; }
        public int DishID { get; set; }
        public string AmountID { get; set; }
        public string NameID { get; set; }
    }

    public partial class Dish
    {
        public int DishID { get; set; }
        public int CategoryID { get; set; }
        public string DishName { get; set; }
    }
    public partial class Recipe
    {
        public int RecipeID { get; set; }
        public int DishID { get; set; }
        public string Description { get; set; }
    }
}

Answer 1

You want to do a left join

To do this you need to do some extra stuff in linq, not sure why it isnt support natively but it isnt.

        var result1 = (
        from d in Dish
        join c in Component on d.DishID equals c.DishID into items
        join r in Recipe on d.DishID equals r.DishID into recipes
        select new Item { 

                     DishID = d.DishID, 

                     components = items.DefaultIfEmpty()
                                       .Where(a=>a!=null)
                                       .ToArray(), 

                     recipe = recipes.DefaultIfEmpty()
                                    .Where(a=>a!=null)
                                    .Select(a=>a.Description)
                                    .FirstOrDefault() 
        }).ToList();