How to yield return inside anonymous methods?

Question

Basically I have an anonymous method that I use for my BackgroundWorker:

worker.DoWork += ( sender, e ) =>
{
    foreach ( var effect in Glob         


        

Answer 1

For new readers: the most elegant way to implement 'anonymous iterators' (i. e. nested in other methods) in C#5 is probably something like this cool trick with async/await (don't be confused by these keywords, the code below is computed absolutely synchronously - see details in the linked page):

        public IEnumerable Numbers()
        {
            return EnumeratorMonad.Build(async Yield =>
            {
                await Yield(11);
                await Yield(22);
                await Yield(33);
            });
        }

        [Microsoft.VisualStudio.TestTools.UnitTesting.TestMethod]
        public void TestEnum()
        {
            var v = Numbers();
            var e = v.GetEnumerator();

            int[] expected = { 11, 22, 33 };

            Numbers().Should().ContainInOrder(expected);

        }

C#7 (available now in Visual Studio 15 Preview) supports local functions, which allow yield return:

public IEnumerable Filter(IEnumerable source, Func filter)
{
    if (source == null) throw new ArgumentNullException(nameof(source));
    if (filter == null) throw new ArgumentNullException(nameof(filter));

    return Iterator();

    IEnumerable Iterator()
    {
        foreach (var element in source) 
        {
            if (filter(element)) { yield return element; }
        }
    }
}