Linq Recursive Sum

CSharp · Console

/Program.cs

using System;
using System.Collections.Generic;
using System.Linq;
					
public class Program
{
	public static void Main()
	{
        var items = new List<Item>
        {
            new Item{ Id = 1, Name = "Machine" },
            new Item{ Id = 3, Id_Parent = 1,  Name = "Machine1"},
            new Item{ Id = 5, Id_Parent = 3,  Name = "Machine1-A", Number = 2, Price = 10 },
            new Item{ Id = 9, Id_Parent = 3,  Name = "Machine1-B", Number = 4, Price = 11 },
            new Item{ Id = 100,  Name = "Item" } ,
            new Item{ Id = 112,  Id_Parent = 100, Name = "Item1", Number = 5, Price = 55 }
        };
		
		foreach(var item in items)
		{
			Console.WriteLine("{0} {1} $" + GetSum(items, item.Id).ToString(), item.Name, item.Id);
		}
		
	}
	
	public static int GetSum(IEnumerable<Item> items, int id)
	{
		// add all matching items
		var itemsToSum = items.Where(i => i.Id == id).ToList();
		var oldCount = 0;
		var currentCount = itemsToSum.Count();
		// it nothing was added we skip the while
		while (currentCount != oldCount)
		{
			oldCount = currentCount;
			// find all matching items except the ones already in the list
			var matchedItems = items
				.Join(itemsToSum, item => item.Id_Parent, sum => sum.Id, (item, sum) => item)
				.Except(itemsToSum)
				.ToList();
			itemsToSum.AddRange(matchedItems);
			currentCount = itemsToSum.Count;
		}
		
		return itemsToSum.Sum(i => i.Price);
	}
	
	public class Item
	{
		public int Id { get; set; }
		public int Id_Parent { get; set; }
		public int Number { get; set; }
		public int Price { get; set; }
		public string Name { get; set; }
	
	}
}