title: List<long> to comma delimited string in C#
body: <p>This often comes up. I have a List and I want to go to a comma delimited string of all the elements in the list that I can use in SQL.</p>
  
  <p>What is the most elegant way to do this in C#? Iterating over all of them is fine, except either the first or last element has to be special-cased since I don't want leading or trailing commas.</p>
  
  <p>Got a good one-liner?</p>