C# - IEnumerable to delimited string

Question

What is the functional programming approach to convert an IEnumerable<string> to a delimited string? I know I can use a loop, but I'm trying to wrap my head around functional programming.

Here's my example:

var selectedValues = from ListItem item in checkboxList.Items where item.Selected select item.Value;  var delimitedString = ?? 

.. or could I do this in just the first var assignment (append each result to the previous)?

Answer 1

string.Join(", ", string[] enumerable) 

Answer 2

Here's an example with a StringBuilder. The nice thing is that Append() returns the StringBuilder instance itself.

  return list.Aggregate( new StringBuilder(),                                 ( sb, s ) =>                                 ( sb.Length == 0 ? sb : sb.Append( ',' ) ).Append( s ) );