Question

I’m trying to set up a validation expression for an ASP.Net Regular Expression Validator control. It is for validating the creation of a user name, so I want to limit the number of characters, and I also want to prevent them from using spaces. Here’s what I’ve got so far:

^.*(?=.{5,20})(?=.*\w{5,255}).*$

The \w{5,255} part prevents spaces and special characters (except for underscores, apparently). I have no idea how “5,255” makes it work, but it does; I just copied it from somewhere else.

The main problem I’m having is that if the first or last character is a space (or special character), it passes validation, which is not acceptable. Can anyone help me? I’m sure it is something simple, but I know next to nothing about regular expressions.

Answer 1

You can use something simpler like this:

^[a-zA-Z0-9_]{5,255}$

This will allow alphanumeric usernames between 5-255 characters in length.