title: Regular Expression: Allow letters, numbers, and spaces (with at least one letter or number)
body: <p>I'm currently using this regex <code>^[A-Z0-9 _]*$</code> to accept letters, numbers, spaces and underscores. I need to modify it to require at least one number or letter somewhere in the string. Any help would be appreciated!</p>
  <p>This would be for validating usernames for my website. I'd actually like to support as many characters as I can, but just want to ensure that I prevent code injection and that characters will display fine for all users. So I'm definitely open to regex validation suggestions that would support a wider set of characters.</p>