Regex accept numeric only. First character can't be 0

Question

I have a textbox that I created using .NET..

By using that textbox, the user only can key in numeric. But not start with 0. start with 1-9. after the user key in th

Answer 1

To match a number starting with any digit but zero:

^[1-9][0-9]*$

And if you want to match 0 as well:

^([1-9][0-9]*)|([0]+)$

remove the last plus if you want a single zero only

To allow any alpha-numeric after first non-zero:

^[1-9a-zA-Z][0-9a-zA-Z]*$