#1,194 – Chaining Iterators Together

An iterator can work on an IEnumerable<T>, using one sequence as input and generating a second sequence from the first.

In the example below, we use the output of one iterator as the input for another iterator.

        static void Main(string[] args)
            IEnumerable<Dog> dogs1 = AllMyDogs();

            foreach (Dog d in dogs1)

            IEnumerable<Dog> dogs2 = YoungDogs(dogs1);

            foreach (Dog d in dogs2)

            IEnumerable<Breed> breeds = BreedsByNamePattern(dogs2, "oo");

            foreach (Breed b in breeds)


        private static IEnumerable<Dog> AllMyDogs()
            yield return new Dog("Kirby", Breed.BorderCollie, 14);
            yield return new Dog("Jack", Breed.JackRussell, 15);
            yield return new Dog("Ruby", Breed.Mutt, 4);
            yield return new Dog("Lassie", Breed.Collie, 12);
            yield return new Dog("Foofoo", Breed.Sheltie, 8);
            yield return new Dog("Pongo", Breed.Dalmatian, 4);
            yield return new Dog("Rooster", Breed.WestHighlandTerrier, 1);

        private static IEnumerable<Dog> YoungDogs(IEnumerable<Dog> dogs)
            foreach (Dog d in dogs)
                if (d.Age < 10)
                    yield return d;

        private static IEnumerable<Breed> BreedsByNamePattern(IEnumerable<Dog> dogs, string pattern)
            foreach (Dog d in dogs)
                if (d.Name.Contains(pattern))
                    yield return d.Breed;



About Sean
Software developer in the Twin Cities area, passionate about .NET technologies. Equally passionate about my own personal projects related to family history and preservation of family stories and photos.

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