Interesting use of the C# yield keyword in Nerd Dinner tutorial

Question

Working through a tutorial (Professional ASP.NET MVC - Nerd Dinner), I came across this snippet of code:

public IEnumerable GetRuleViolation         


        

Answer 1

Short version:

1: The yield is the magic "Stop and come back later" keyword, so the if statements in front of the "active" one have been evaluated.

2: yield break explicitly ends the enumeration (think "break" in a switch case)

3: Every time. You can cache the result, of course, by turning it into a List for example and iterating over that afterwards.