Here's a way to do it in one line of Linq code:
int score = System.IO.File.ReadAllLines(ConfigurationManager.AppSettings["LocationOfNamesFile"])
.SelectMany(s => s.Split(','))
.OrderBy(b => b)
.Select((s, i) => new {
Index = i + 1,
Score = s.Sum(ch => (int)(char.ToUpper(ch) - 'A' + 1))
.Sum(s => s.Index * s.Score);
This will throw an exception if the file doesn't exist, but your original code does this as well.