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\"

Answer 1

Or slightly less verbose than the accepted answer:

^[a-zA-Z][\w]*$

C# regex has character class indicator "\w" for alphanumeric characters, but does not have a character class for just alphabetic (no digits), hence you have to specify class set [a-zA-Z] manually.