using System;

public class Program

{

    public static void Main()

    {

        dynamic a = 17.3;

        var result = (a is Double) ? a : null;

        Console.WriteLine("Result " + Convert.ToString(result));

        dynamic b = "NaN";

        var result2 = (b is Double) ? b : null;

        Console.WriteLine("Result " + Convert.ToString(result2));

    }

}