Identify if a string is a number

Question

If I have these strings:

1. \"abc\" = false

2. \"123\" = true

3. \"ab2\"

Answer 1

Try the reges below

new Regex(@"^\d{4}").IsMatch("6")    // false
new Regex(@"^\d{4}").IsMatch("68ab") // false
new Regex(@"^\d{4}").IsMatch("1111abcdefg")
new Regex(@"^\d+").IsMatch("6") // true (any length but at least one digit)