C# Regex to allow only alpha numeric

Question

I have the following regex ^[a-zA-Z0-9]+$ which would allow alpha numeric characters. The problem here is that if I enter only numeric character like "897687", then the regex still matches. I don't want that to happen. There should be at least one text character and it should start with a text character. For example like "a343" or "a98bder" or "a4544fgf343"

It would be great if you could help me to improve my regex for this.

Answer 1

Sounds like you want:

^[a-zA-Z][a-zA-Z0-9]*$ 

EXPLANATION

^ asserts position at the start of a line

Match a single character present in the list below [a-zA-Z]

» a-z a single character in the range between a (index 97) and z (index 122) (case sensitive)

» A-Z a single character in the range between A (index 65) and Z (index 90) (case sensitive)

Match a single character present in the list below [a-zA-Z0-9]*

* Quantifier — Matches between zero and unlimited times, as many times as possible, giving back as needed (greedy)

a-z a single character in the range between a (index 97) and z (index 122) (case sensitive)

A-Z a single character in the range between A (index 65) and Z (index 90) (case sensitive)

0-9 a single character in the range between 0 (index 48) and 9 (index 57) (case sensitive)

$ asserts position at the end of a line

Demo