C# : To return a comma delimited list from an array or collection of strings

Don't:
[csharp]
var description = new StringBuilder("");
foreach (var item in productItems.Where(x => x.ItemType == type))
{
description.Append(item.Description + ", ");
}
return description.Remove(description.Length - 2, 2).ToString();
[/csharp]
Do:
[csharp]
return string.Join(", ", productItems.Where(x => x.ItemType == type).Select(x => x.Description).ToArray());
[/csharp]
because the first example fails when your collection has no elements.