Cleaning up code with Regular Expressions

[bixel]

I am terrible at knowing regular expressions very well so mostly I find examples then try to use them, however my code usually ends up being really ugly even though it works.

                string classifications = LineNode.InnerText;
                //Makes This_TypeOfStringIsLong > This_Type Of String Is Long
                string spaced = Regex.Replace(classifications, @"([a-z])([A-Z])", @"$1 $2", RegexOptions.None);
                //Makes This_Type Of String Is Long > This_Type,Of,String,Is,Long
                string modded = spaced.Replace(" ", ",");
                //Makes This_Type,Of,String,Is,Long > This Type,Of,String,Is,Long
                string again = modded.Replace("_", " ");
                string[] LineArray = again.Split(',');

Is there a simple shorter way of doing this?

we begin with a string like "This_TypeOfStringIsLong" has to be parsed out by each Capital Word, then if there is a _ make a space, but its original word has to be treated as one

example Blue_SkyDarkNightOwl > Blue Sky, Dark, Night, Owl