Regex that accept AlphaNumeric as first & last character and accept having AlphaNumeric with only 0 or 1 hyphen in the middle

I am trying to update the current regex ^[^-]*-?[^-]*$ to take AlphaNumeric only for the first & last character and accept having AlphaNumeric with only 0 or 1 hyphen in the middle in regex C#.

Please check below the valid and invalid values.

Invalid values:

-A
B2-
A--B
#12

Valid values:

A
A-B
"" // empty
1A
12

Please advise?

Thank you,

>Solution :

You can make the whole pattern optional, and only allow starting with chars A-Z 0-9 with an optional part for - and again chars A-Z 0-9:

 ^(?:[A-Z0-9]+(?:-[A-Z0-9]+)?)?$

If the match should be case insensitive, you can either use [a-zA-Z0-9] or start the pattern with (?i)

Explanation

• ^ Start of string
• (?: Non capture group
  • [A-Z0-9]+ Match 1+ chars A-Z0-9
  • (?:-[A-Z0-9]+)? Optionally match - and 1+ chars A-Z0-9
• )? Close the non capture group and make the whole part optional
• $ End of string

Regex demo

Or matching any kind of letter and any kind of number:

^(?:^[\p{L}\p{N}]+(?:-[\p{L}\p{N}]+)?)?$

Regex demo