I wanted to bring this challenge to the attention of the stackoverflow community. The original problem and answers are here. BTW, if you did not follow it before, you should
public static string CommaQuibbling(IEnumerable items)
{
var itemArray = items.ToArray();
var commaSeparated = String.Join(", ", itemArray, 0, Math.Max(itemArray.Length - 1, 0));
if (commaSeparated.Length > 0) commaSeparated += " and ";
return "{" + commaSeparated + itemArray.LastOrDefault() + "}";
}