Transformar Temperatura

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using Microsoft.Phone.Controls;

namespace PhoneApp1
{
    public partial class Newton : PhoneApplicationPage
    {
        public Newton()
        {
            InitializeComponent();
        }

        private void OK_Click(object sender, RoutedEventArgs e)
        {
            double a = 0, b = 0, c = 0;
            a = (((double.Parse(TempNewton.Text) * 60) / 11) + 32);
            b = (((double.Parse(TempNewton.Text)) * 100)/ 33);
            c = (((double.Parse(TempNewton.Text) * 100) / 33) + 273.15);


            {
                RFahrenheit.Text = a.ToString();
                RCelsius.Text = b.ToString();
                RNewton.Text = c.ToString();
            }
        }

        private void negativo_Click(object sender, RoutedEventArgs e)
        {
            if (TempNewton.Text.StartsWith("-"))
                TempNewton.Text = TempNewton.Text.Substring(1);
            else
                TempNewton.Text = "-" + TempNewton.Text;
        }

        private void button1_Click(object sender, RoutedEventArgs e)
        {
        NavigationService.GoBack();
        }
        protected override void OnBackKeyPress(System.ComponentModel.CancelEventArgs e)
        {
            base.OnBackKeyPress(e);
            if (TempNewton.Text != string.Empty)
            {
                var result = MessageBox.Show("Tem certeza que quer sair?",
                "Aviso", MessageBoxButton.OKCancel);
                if (result != MessageBoxResult.OK)
                {
                    e.Cancel = true;
                }
            }
        }
    }
}