Question

Consider the need for a function in C# that will test whether a string is a numeric value.

The requirements:

• must return a boolean.
• function should be able to allow for whole numbers, decimals, and negatives.
• assume no using Microsoft.VisualBasic to call into IsNumeric(). Here’s a case of reinventing the wheel, but the exercise is good.

Current implementation:

 //determine whether the input value is a number
    public static bool IsNumeric(string someValue)
    {
        Regex isNumber = new Regex(@"^\d+$");
        try
        {
            Match m = isNumber.Match(someValue);
            return m.Success;                           
        }
        catch (FormatException)
        {return false;}
    }

Question: how can this be improved so that the regex would match negatives and decimals? Any radical improvements that you’d make?

Answer 1

Just off of the top of my head – why not just use double.TryParse ? I mean, unless you really want a regexp solution – which I’m not sure you really need in this case 🙂