Calculadora en c#

Este es un proyecto de una Calculadora en WPF :

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//Codigo archivo: MainWindows.xaml

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<Window x:Class="CalculadoraWPF.MainWindow"

        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"

        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"

        xmlns:local="clr-namespace:CalculadoraWPF"

        mc:Ignorable="d"

        Title="Calculadora WPF" Height="400" Width="355">

    <Grid>

        <TextBox x:Name="Textbox_Screen" IsReadOnly="True" TextAlignment="Right" VerticalContentAlignment="Center" HorizontalAlignment="Left" Height="50" Margin="15,28,0,0" TextWrapping="NoWrap" VerticalAlignment="Top" Width="310" FontSize="40" FontWeight="Bold" MaxLength="15" MaxLines="15"/>

        <Button Content="7" HorizontalAlignment="Left" Margin="15,105,0,0" VerticalAlignment="Top" Width="50" Height="50" Click="Presiona_Siete" FontSize="24" FontWeight="Bold"/>

        <Button Content="/" HorizontalAlignment="Left" Margin="210,300,0,0" VerticalAlignment="Top" Width="50" Height="50" Click="Presiona_Dividir" FontSize="24" FontWeight="Bold"/>

        <Button Content="*" HorizontalAlignment="Left" Margin="210,235,0,0" VerticalAlignment="Top" Width="50" Height="50" Click="Presiona_Multiplicar" FontWeight="Bold" FontSize="24"/>

        <Button Content="-" HorizontalAlignment="Left" Margin="210,170,0,0" VerticalAlignment="Top" Width="50" Height="50" Click="Presiona_Restar" FontSize="24" FontWeight="Bold"/>

        <Button Content="=" HorizontalAlignment="Left" Margin="145,300,0,0" VerticalAlignment="Top" Width="50" Height="50" Click="Presiona_Igual" FontSize="24" FontWeight="Bold"/>

        <Button Content="3" HorizontalAlignment="Left" Margin="145,235,0,0" VerticalAlignment="Top" Width="50" Height="50" Click="Presiona_Tres" FontSize="24" FontWeight="Bold"/>

        <Button Content="6" HorizontalAlignment="Left" Margin="145,170,0,0" VerticalAlignment="Top" Width="50" Height="50" Click="Presiona_Seis" FontSize="24" FontWeight="Bold"/>

        <Button Content="." HorizontalAlignment="Left" Margin="80,300,0,0" VerticalAlignment="Top" Width="50" Height="50" Click="Presiona_Punto" FontSize="24" FontWeight="Bold"/>

        <Button Content="2" HorizontalAlignment="Left" Margin="80,235,0,0" VerticalAlignment="Top" Width="50" Height="50" Click="Presiona_Dos" FontWeight="Bold" FontSize="24"/>

        <Button Content="5" HorizontalAlignment="Left" Margin="80,170,0,0" VerticalAlignment="Top" Width="50" Height="50" Click="Presiona_Cinco" FontSize="24" FontWeight="Bold"/>

        <Button Content="0" HorizontalAlignment="Left" Margin="15,301,0,0" VerticalAlignment="Top" Width="50" Height="50" Click="Presiona_Cero" FontSize="24" FontWeight="Bold"/>

        <Button Content="1" HorizontalAlignment="Left" Margin="15,235,0,0" VerticalAlignment="Top" Width="50" Height="50" Click="Presiona_Uno" FontSize="24" FontWeight="Bold"/>

        <Button Content="4" HorizontalAlignment="Left" Margin="15,170,0,0" VerticalAlignment="Top" Width="50" Height="50" Click="Presiona_Cuatro" FontSize="24" FontWeight="Bold"/>

        <Button Content="8" HorizontalAlignment="Left" Margin="80,105,0,0" VerticalAlignment="Top" Width="50" Height="50" Click="Presiona_Ocho" FontSize="24" FontWeight="Bold"/>

        <Button Content="9" HorizontalAlignment="Left" Margin="145,105,0,0" VerticalAlignment="Top" Width="50" Height="50" Click="Presiona_Nueve" FontSize="24" FontWeight="Bold"/>

        <Button Content="+" HorizontalAlignment="Left" Margin="210,105,0,0" VerticalAlignment="Top" Width="50" Height="50" Click="Presiona_Sumar" FontSize="24" FontWeight="Bold"/>

        <Button Content="C" HorizontalAlignment="Left" Margin="275,105,0,0" VerticalAlignment="Top" Width="50" Height="50" Click="Presiona_Clear" FontSize="24" FontWeight="Bold"/>

    </Grid>

</Window>

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//Codigo archivo: MainWindows.xaml.cs

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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 CalculadoraWPF

{

    /// <summary>

    /// Interaction logic for MainWindow.xaml

    /// </summary>

    public partial class MainWindow : Window

    {

        double primera_Entrada;

        double segunda_Entrada;

        double resultado;

        string operador;

        public MainWindow()

        {

            InitializeComponent();

        }

        private void Presiona_Cero(object sender, RoutedEventArgs e)

        {

            Textbox_Screen.Text = Textbox_Screen.Text + "0"; 

        }

        private void Presiona_Uno(object sender, RoutedEventArgs e)

        {

            Textbox_Screen.Text = Textbox_Screen.Text + "1";

        }

        private void Presiona_Dos(object sender, RoutedEventArgs e)

        {

            Textbox_Screen.Text = Textbox_Screen.Text + "2";

        }

        private void Presiona_Tres(object sender, RoutedEventArgs e)

        {

            Textbox_Screen.Text = Textbox_Screen.Text + "3";

        }

        private void Presiona_Cuatro(object sender, RoutedEventArgs e)

        {

            Textbox_Screen.Text = Textbox_Screen.Text + "4";

        }

        private void Presiona_Cinco(object sender, RoutedEventArgs e)

        {

            Textbox_Screen.Text = Textbox_Screen.Text + "5";

        }

        private void Presiona_Seis(object sender, RoutedEventArgs e)

        {

            Textbox_Screen.Text = Textbox_Screen.Text + "6";

        }

        private void Presiona_Siete(object sender, RoutedEventArgs e)

        {

            Textbox_Screen.Text = Textbox_Screen.Text + "7";

        }

        private void Presiona_Ocho(object sender, RoutedEventArgs e)

        {

            Textbox_Screen.Text = Textbox_Screen.Text + "8";

        }

        private void Presiona_Nueve(object sender, RoutedEventArgs e)

        {

            Textbox_Screen.Text = Textbox_Screen.Text + "9";

        }

        private void Presiona_Sumar(object sender, RoutedEventArgs e)

        {

            operador = "+";

            primera_Entrada = double.Parse(Textbox_Screen.Text);

            Textbox_Screen.Clear();

        }

        private void Presiona_Restar(object sender, RoutedEventArgs e)

        {

            operador = "-";

                primera_Entrada = double.Parse(Textbox_Screen.Text);

                Textbox_Screen.Clear();

        }

        private void Presiona_Multiplicar(object sender, RoutedEventArgs e)

        {

            operador = "*";

            primera_Entrada = double.Parse(Textbox_Screen.Text);

            Textbox_Screen.Clear();

        }

        private void Presiona_Dividir(object sender, RoutedEventArgs e)

        {

            operador = "/";

            primera_Entrada = double.Parse(Textbox_Screen.Text);

            Textbox_Screen.Clear();

        }

        private void Presiona_Punto(object sender, RoutedEventArgs e)

        {

            if (Textbox_Screen.Text.Contains("."))

            {

            }

            else

            {

                Textbox_Screen.Text = Textbox_Screen.Text + ".";

            }

        }

        private void Presiona_Igual(object sender, RoutedEventArgs e)

        {

            segunda_Entrada = double.Parse(Textbox_Screen.Text);

            switch (operador)

            {

                case "+":

                    resultado = primera_Entrada + segunda_Entrada;

                    Textbox_Screen.Text = resultado.ToString();

                    break;

                case "-":

                    resultado = primera_Entrada - segunda_Entrada;

                    Textbox_Screen.Text = resultado.ToString();

                    break;

                case "*":

                    resultado = primera_Entrada * segunda_Entrada;

                    Textbox_Screen.Text = resultado.ToString();

                    break;

                case "/":

                    resultado = primera_Entrada / segunda_Entrada;              

                    Textbox_Screen.Text = resultado.ToString();

                    break;

            }

        }

        private void Presiona_Clear(object sender, RoutedEventArgs e)

        {

            Textbox_Screen.Clear();

        }

    }

}