C# Regex – Replacing Spaces Inside Strings

I like to use:

myString = Regex.Replace(myString, @"\s+", " ");

Since it will catch runs of any kind of whitespace (e.g. tabs, newlines, etc.) and replace them with a single space.

- denotes a character range, just as you use A-Z to describe any character between A and Z. Your regex uses ñ-\s which the engine tries to interpret as any character between ñ and \s -- and then notices, that \s doesn't make a whole lot of sense there, because \s itself is only an abbreviation for any whitespace character.

That's where the error comes from.

To get rid of this, you should always put - at the end of your character class, if you want to include the - literal character:

@"^[a-zA-Zàéèêçñ\s][a-zA-Zàéèêçñ\s-]+$"

This way, the engine knows that \s- is not a character range, but the two characters \s and - seperately.

The other way is to escape the - character:

@"^[a-zA-Zàéèêçñ\s][a-zA-Zàéèêç\-\s]+$"

So now the engine interprets ñ\-\s not as a character range, but as any of the characters ñ, - or \s. Personally, though I always try to avoid escaping as often as possible, because IMHO it clutters up and needlessly stretches the expression in length.