Is there a Linq method to add a single item to an IEnumerable?

Question

Basically I am trying to do something like this:

image.Layers

which returns an IEnumerable for all layers except the Parent layer,

Answer 1

There is no single method which does this. The closest is the Enumerable.Concat method but that tries to combine an IEnumerable with another IEnumerable. You can use the following to make it work with a single element

image.Layers.Concat(new [] { image.ParentLayer });

Or just add a new extension method

public static IEnumerable ConcatSingle(this IEnumerable enumerable, T value) {
  return enumerable.Concat(new [] { value });
}