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yield return hands back a value. yield break says there are no more values and ends the sequence — it is the return; of an iterator.

static IEnumerable<string> ReadUntilBlank(string[] lines)
{
    foreach (var line in lines)
    {
        if (string.IsNullOrWhiteSpace(line))
        {
            yield break;
        }

        yield return line.Trim();
    }
}

Falling off the end of the method does the same thing, so yield break earns its place only when you want to stop from inside a branch.

You can also yield from several places. There is no rule that an iterator has one yield return:

static IEnumerable<string> Envelope(string body)
{
    yield return "--- begin ---";
    yield return body;
    yield return "--- end ---";
}

Do not reach for plain return

yield return is not a return. A return with a value is illegal in an iterator — the method already declared what it produces by yielding. Write yield break when you mean "stop".

Try it: Task 2

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