Fastest way to check if string contains only digits

Question

I know a few ways how to check this. regex,int.parse,tryparse,looping.

can anyone tell me what is the fastest way to check?

the nee

Answer 1

I like Linq and to make it exit on first mismatch you can do this

string str = '0129834X33';
bool isAllDigits = !str.Any( ch=> ch < '0' || ch > '9' );