Question

I have different cases:

1. No spaces allowed at all
2. No spaces allowed at the beginning or the end of the string only

..A little question, is it good to check (to validate) the input for spaces through the RegEx of the RegularExpressionValidator ?

Answer 1

In your previous question, you mentioned you wanted from 0 to 50 characters. If that’s still the case, here’s what you want:

/^\S{0,50}$/
/^(?!\s).{0,50}(?<!\s)$/

As of right now, I think these are the only regexes posted that allow for less than one letter with the first pattern, and less than two letters with the second pattern.

Regexes are not a “bad” thing, they’re just a specialized tool that isn’t suited for every task. If you’re trying to validate input in ASP.NET, I would definitely use a RegularExpressionValidator for this particular pattern, because otherwise you’ll have to waste your time writing a CustomValidator for a pretty meager performance boost. See my answer to this other question for a little guidance on when and when not to use regex.

In this case, the reason I’d use a regex validator has less to do with the pattern itself and more to do with ASP.NET. A RegularExpressionValidator can just be dragged and dropped into your ASPX code, and all you’d have to write would be 10-21 characters of regex. With a CustomValidator, you’d have to write custom validation functions, both in the codebehind and the JavaScript. You might squeeze a little more performance out of it, but think about when validation comes into play: only once per postback. The performance difference is going to be less than a millisecond. It’s simply not worth your time as a developer — to you or your employer. Remember: Hardware is cheap, programmers are expensive, and premature optimization is the root of all evil.