Mileage WPF (Evening)

Here is the Mileage class

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace MileageForm
{
    /// 

    /// this is a very simple mileage class 
    /// it has three properties
    /// Distance, Gallons and PricePerGallon
    /// I used a short cut method to create
    /// the properties just expressing the get and set
    /// It has two methods one to calculate 
    /// the gas mileage and one to calculate the 
    /// price per mile
    /// 
    class Mileage
    {
        //short cut for properties
         public double Distance {get; set;}
         public double Gallons { get; set; }
         public double PricePerGallon { get; set; }

        //methods
        public double CalculateMileage()
         {
             return Distance / Gallons;
         }

        public double CalculatePricePerMile()
        {
            return  PricePerGallon * Gallons /Distance;
        }

    } 
}

Here is the XAML for the form

<Window x:Class="MileageForm.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525"
        Name="Form1">
    <Grid x:Name="labelCost">
        <Label Content="Enter the miles traveled" HorizontalAlignment="Left" Margin="46,7,0,0" VerticalAlignment="Top"/>
        <TextBox x:Name="textMiles" HorizontalAlignment="Left" Height="23" Margin="227,11,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="120"/>
        <Label Content="Enter the total gallons" HorizontalAlignment="Left" Margin="46,55,0,0" VerticalAlignment="Top"/>
        <TextBox x:Name="textGallons" HorizontalAlignment="Left" Height="23" Margin="227,55,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="120"/>
        <Label Content="Enter the price per Gallon" HorizontalAlignment="Left" Margin="46,98,0,0" VerticalAlignment="Top"/>
        <TextBox x:Name="textPrice" HorizontalAlignment="Left" Height="23" Margin="227,98,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="120"/>
        <Button x:Name="ButtonCalculate" Content="Calculate" HorizontalAlignment="Left" Margin="56,142,0,0" VerticalAlignment="Top" Width="75" Click="ButtonCalculate_Click"/>
        <Label Content="Your Mileage is" HorizontalAlignment="Left" Margin="46,181,0,0" VerticalAlignment="Top"/>
        <Label x:Name="labelMileage" Content="Label" HorizontalAlignment="Left" Margin="227,181,0,0" VerticalAlignment="Top" RenderTransformOrigin="0.474,-0.385"/>
        <Label Content="The cost per mile is" HorizontalAlignment="Left" Margin="46,212,0,0" VerticalAlignment="Top"/>
        <Label x:Name="labelCost1" Content="Label" HorizontalAlignment="Left" Margin="227,220,0,0" VerticalAlignment="Top" RenderTransformOrigin="-0.026,0.385"/>
        <Button x:Name="buttonClear" Content="Clear" HorizontalAlignment="Left" Margin="56,259,0,0" VerticalAlignment="Top" Width="75" Click="buttonClear_Click"/>
        <Button x:Name="buttonExit" Content="Exit" HorizontalAlignment="Left" Margin="156,259,0,0" VerticalAlignment="Top" Width="75" Click="buttonExit_Click"/>

    </Grid>
</Window>

Here is the code behind the form

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace MileageForm
{
    /// 

    /// Interaction logic for MainWindow.xaml
    /// this is the code behind the windows form
    /// 
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            //initilize the form--don't remove thos
            InitializeComponent();
        }

        private void ButtonCalculate_Click(object sender, RoutedEventArgs e)
        {

            //call the method to make sure the text boxes have content
            //they return true if there is a value missing
            bool good =CheckTextBoxes();
            //if there is a value missing stop the action
            //here
            if (good)
            {
                return;
            }
            //delcare a new instance of Mileage class
            Mileage m = new Mileage();
            //get inputs
            m.Distance = double.Parse(textMiles.Text);
            m.Gallons = double.Parse(textGallons.Text);
            m.PricePerGallon = double.Parse(textPrice.Text);
            //outputs
            labelMileage.Content = m.CalculateMileage().ToString();
            EvaluateMileage(m.CalculateMileage());
            labelCost1.Content= m.CalculatePricePerMile().ToString("C");

        }

        private void buttonClear_Click(object sender, RoutedEventArgs e)
        {
            //this method clears the textboxes and labels
            textMiles.Clear();
            textGallons.Clear();
            textPrice.Clear();
            labelCost1.Content="";
            labelMileage.Content = "";
            //resets the color to white
            Form1.Background = new SolidColorBrush(Colors.White);
            textMiles.Focus();
        }

        private void buttonExit_Click(object sender, RoutedEventArgs e)
        {
            //close the form
            this.Close();
            
        }

        private void EvaluateMileage(double mileage)
        {
            //this checks the mileage and returns a 
            //background color based on the value
            if (mileage > 35)
            {
                Form1.Background = new SolidColorBrush(Colors.Green);
            }
            else if (mileage > 25)
            {
                Form1.Background = new SolidColorBrush(Colors.Yellow);
            }
            else
            {
                Form1.Background = new SolidColorBrush(Colors.Red);
            }
        }

        private bool CheckTextBoxes()
        {
           //this method checks to make sure the form
            //textboxes have values
            if (textMiles.Text=="")
            {
                MessageBox.Show("Enter a valid mileage");
                return true;
            }
            if(textGallons.Text=="")
            {
                MessageBox.Show("Enter a valid Gallon amount");
               return true;
            }
            if (textPrice.Text == "")
            {
                MessageBox.Show("Enter a valid Price per Gallon");
                return true;
            }
            return false;
        }
    }
}

Here is a picture of the form in design