Here's an extension method that I have used extensively for this kind of thing
public static string SplitCamelCase( this string str )
{
return Regex.Replace(
Regex.Replace(
str,
@"(\P{Ll})(\P{Ll}\p{Ll})",
"$1 $2"
),
@"(\p{Ll})(\P{Ll})",
"$1 $2"
);
}
It also handles strings like IBMMakeStuffAndSellIt, converting it to IBM Make Stuff And Sell It (IIRC).
Syntax explanation (credit):
{Ll} is Unicode Character Category "Letter lowercase" (as opposed to {Lu} "Letter uppercase"). P is a negative match, while p is a positive match, so \P{Ll} is literally "Not lowercase" and p{Ll} is "Lowercase".
So this regex splits on two patterns. 1: "Uppercase, Uppercase, Lowercase" (which would match the MMa in IBMMake and result in IBM Make), and 2. "Lowercase, Uppercase" (which would match on the eS in MakeStuff). That covers all camelcase breakpoints.
TIP: Replace space with hyphen and call ToLower to produce HTML5 data attribute names.