Finding an object in a list, remove and return it [duplicate]

Question

Possible Duplicate:
c#: how do I remove an Item inside IEnumerable

I have an Inumerable of Objects foo.

 public IEnumerable<foo> listOfFoo{ get; set; }

Foo has Id and name lets say.

I want to pass an ID to a method and the method should remove the object with that ID from the IEnumerable and return it.

Whats the best way of doing it?

Answer 1

IEnumerables are read-only. You can't remove an object from one.

That said, you could do something like

public Foo QuoteRemoveUnquoteById(int id)
{
    var rtnFoo = listOfFoo.SingleOrDefault(f => f.Id == id);
    if (rtnFoo != default(Foo))
    {
        listOfFoo = listOfFoo.Where(f => f.Id != id);
    }
    return rtnFoo;
}

which just masks out the matching Foo? However, this will get less and less performant the more items you "remove". Also, anything else that holds a reference to listOfFoo won't see any change.

Answer 2

That's not possible for any collection that implements IEnumerable<foo>. If it is for example a List<foo>, then it's possible to remove items for it, but if it is for example a foo[] it's not possible to remove items.

If you use a List<foo> instead:

public foo Extract(int id) {
  int index = listOfFoo.FindIndex(x => x.Id == id);
  foo result = listOfFoo[index];
  listOfFoo.removeAt(index);
  return result;
}