Provides a function that will allow two imprecise floating point numbers to be compared for "near" equality and also an "IsNumeric" function.

NumericHelpers.cs

public static class NumericHelpers
    {
        // Float point maths is whack.  We can't check for absolute equality as floating point numbers are imprecise
        // and are subject to rounding issues (See: http://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html)
        // Therefore, we can't check for absolute equality, but instead we have to need to check for values being
        // "nearly" equal, which allows a small margin of error (i.e. something known as the "Epsilon" value for
        // the given data type for this CPU that this code is running on).
        public static bool NearlyEqual(double a, double b, double epsilon)
        {
            var absA = Math.Abs(a);
            var absB = Math.Abs(b);
            var diff = Math.Abs(a - b);

            if (a == b)
            {
                // shortcut, handles infinities
                return true;
            }
            if (a == 0 || b == 0 || diff < double.Epsilon)
            {
                // a or b is zero or both are extremely close to it
                // relative error is less meaningful here
                return diff < epsilon;
            }
            // use relative error
            return diff / (absA + absB) < epsilon;
        }

        public static bool IsNumeric(object expression)
        {
            if (expression == null)
            {
                return false;
            }
            double number;
            return double.TryParse(Convert.ToString(expression, CultureInfo.InvariantCulture), NumberStyles.Any, NumberFormatInfo.InvariantInfo, out number);
        }
    }