Question

I need to use C# to write a Regular Expression for a title, here is the requirement:

1. Title is required (length > 0);
2. Maximum 256 characters (length <= 256);
3. No character is forbidden, but whitespace only is illegal (the title ONLY containing whitespaces is illegal);
4. No leading or trailing whitespaces;

I have already have this:

^.{1,256}$

So how can I meet the rule 3?

EDIT:

1. Explained rule 3 more clearly;
2. I added rule 4 from Mario’s answer.

Answer 1

I’d skip regular expressions completely, because you can just hardcode string cleanup and validation in two simple steps:

• Use String.Trim(null) to remove all leading/trailing whitespaces.
• Compare the length of the remaining string.
• Uppercase the first character (if you want to).

This works, because a name consisting of whitespaces only would be trimmed to 0 length.
Also this avoids using titles such as " Let's go!".