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

This might be coming super late!, but I'm sure it will help someone, as it helped me.

        private static bool IsDigitsOnly(string str)
        {
            return str.All(c => c >= '0' && c <= '9');
        }