Identify if a string is a number

Question

If I have these strings:

1. \"abc\" = false

2. \"123\" = true

3. \"ab2\"

Answer 1

If you want to check if a string is a number (I'm assuming it's a string since if it's a number, duh, you know it's one).

• Without regex and
• using Microsoft's code as much as possible

you could also do:

public static bool IsNumber(this string aNumber)
{
     BigInteger temp_big_int;
     var is_number = BigInteger.TryParse(aNumber, out temp_big_int);
     return is_number;
}

This will take care of the usual nasties:

• Minus (-) or Plus (+) in the beginning
• contains decimal character BigIntegers won't parse numbers with decimal points. (So: BigInteger.Parse("3.3") will throw an exception, and TryParse for the same will return false)
• no funny non-digits
• covers cases where the number is bigger than the usual use of Double.TryParse

You'll have to add a reference to System.Numerics and have using System.Numerics; on top of your class (well, the second is a bonus I guess :)