C#定义常量

using System;

namespace DeclaringConstants {

    class Program {

        static voID Main(string[] args) {
            const double pi = 3.14159;   

            // constant declaration 
            double r;
            Console.Writeline("Enter Radius: ");
            r = Convert.Todouble(Console.Readline());
            double areaCircle = pi * r * r;
            Console.Writeline("Radius: {0}, Area: {1}", r, areaCircle);
            Console.Readline();
        }
    }
}