Question

i have an IList<Animals> farmAnimals;

this list has three types,

• Cows
• Sheep
• Chickens

how can i remove all the Chickens from the list using a lambda query or linq-to-objects so i have a separate list of chickens and the original list now only has cows and sheep.

Do i have to make three lists (the original + 2 new ones, filtered) and then null the original list? or is there a trickier way?

result needs to be

IList<Aniamls> chickens; IList<Animals> farmAnimals; // only contains the cows and sheep, now. 

cheers!

CLARIFICATION QUESTION:

what is more performant? FindAll & RemoveAll versus the Where suggestion?

Answer 1

Assuming:

public abstract class Animal {}  public class Chicken : Animal {} 

you can do:

var chickens = animals.OfType<Chicken>().Cast<Animal>().ToList();  var nonChickens = animals.Except(chickens).ToList(); 

Edit

Any reasonable answer should be O(n), meaning each item in the original list is only processed once. Therefore, I would suggest an imperative approach:

var chickens = new List<Animal>(); var nonChickens = new List<Animal>();  foreach(var animal in animals) {     var list = animal is Chicken ? chickens : nonChickens;      list.Add(animal); }