class CWährungsrechner
    {
        public readonly double euro_dollar_kurs;  // readonly Variable

        public CWährungsrechner(double eurodollarkurs)
        {
        euro_dollar_kurs = eurodollarkurs;
        }
        public double w_umrechnung_euro_dollar(double betrag)
        {
            return betrag / euro_dollar_kurs;
        }
        public double w_umrechnung_dollar_euro(double betrag)
        {
            return betrag * euro_dollar_kurs;
        }
//klasse

//haupt
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace Windows_Forms_Währungsrechner
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            textBox_kurs.Text = "1,35";
            textBox_betrag_euro.Text = "1,00";
            textBox_betrag_dollar.Text= "1,00";

        }

        private CWährungsrechner berechnen;
        private void button4_Click(object sender, EventArgs e)
        {
            Close();
        }



        private void button3_Click(object sender, EventArgs e)
        {
            double euro_dollar_kurs = Convert.ToDouble(textBox_kurs.Text);
            berechnen = new CWährungsrechner(euro_dollar_kurs);
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void button1_Click(object sender, EventArgs e)
        {
            double EURO;
            double DOLLAR;

            EURO = Convert.ToDouble(textBox_betrag_euro.Text);
            DOLLAR = berechnen.w_umrechnung_euro_dollar(EURO);
            textBox_betrag_dollar.Text = Convert.ToString(DOLLAR);
        }

        private void button2_Click(object sender, EventArgs e)
        {
            double EURO;
            double DOLLAR;

            EURO = Convert.ToDouble(textBox_betrag_euro);
            DOLLAR = berechnen.w_umrechnung_dollar_euro(EURO);
            textBox_betrag_euro.Text = Convert.ToString(EURO);
        }



    }
}