This probably has a simple answer, but I must not have had enough coffee to figure it out on my own:
If I had a comma delimited string such as:
string li
I can't write C# code, but this simple JavaScript code is probably easy to adapt:
var s = "Fred,Sam,Mike,Sarah"; alert(s.replace(/\b/g, "'"));
It just replace bounds (start/end of string, transition from word chars non punctuation) by single quote.