// Classe
using System;

namespace Course
{
    class Retangulo
    {
        public double Altura;
        public double Largura;
        public double Area()
        {
            return Largura * Altura;
        }
        public double Perimetro()
        {
            return 2 * (Largura + Altura);
        }
        public double Diagonal()
        {
            return Math.Sqrt(Largura * Largura + Altura * Altura);
        }
    }
}

//_____________________________________

using System;
using System.Globalization;

namespace Course
{
    class Program
    {
        static void Main(string[] args)
        {
            Retangulo ret = new Retangulo();

            Console.WriteLine("Entre a largura e altura do Retângulo: ");
            ret.Largura = double.Parse(Console.ReadLine(), CultureInfo.InvariantCulture );
            ret.Altura  = double.Parse(Console.ReadLine(), CultureInfo.InvariantCulture);

            Console.WriteLine("ÁREA = " + ret.Area().ToString ("F2",CultureInfo.InvariantCulture));
            Console.WriteLine("PERÍMETRO = " + ret.Perimetro().ToString ("F2", CultureInfo.InvariantCulture ));
            Console.WriteLine("DIAGONAL = " + ret.Diagonal().ToString("F2", CultureInfo.InvariantCulture));
        }
    }
}