C# Basic App Updater

mainwindow.xaml.cs

using System;
using System.ComponentModel;
using System.IO;
using System.Net;
using System.Windows;

namespace Basic_Updater_Example
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public string version = "2.1";

        public MainWindow()
        {
            InitializeComponent();

            ClientVersion.Text = "Your App Version: " + version;
        }

        /// <summary>
        /// Update Check Button
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void Button_Click(object sender, RoutedEventArgs e)
        {
            // cerate ne web client for web request
            WebClient webclient = new WebClient();
            // open and read web page
            Stream stream = webclient.OpenRead("http://localhost/updatecheck.php?version=" + version);
            // stream content
            StreamReader reader = new StreamReader(stream);
            // get result
            string result = reader.ReadToEnd();

            if (result == "OK")
            {
                // ask to user would you like download this update/s
                if (MessageBox.Show("Do you want to update application?", "There is an update", MessageBoxButton.YesNo, MessageBoxImage.Question) == MessageBoxResult.Yes)
                {
                    DownloadUpdate();
                }
            } else if (result == "NO")
            {
                // say no update
                MessageBox.Show("Your app is Up to date", "There is not an update", MessageBoxButton.OK, MessageBoxImage.Information);
            } else if (result == "RETURN")
            {
                // ask to user would you like download this update/s
                if (MessageBox.Show("Do you want to update application?", "There is an update", MessageBoxButton.YesNo, MessageBoxImage.Question) == MessageBoxResult.Yes)
                {
                    DownloadUpdate();
                }
            }
        }

        /// <summary>
        /// Update Downloader Method
        /// </summary>
        public void DownloadUpdate()
        {
            // cerate ne web client for file download
            WebClient webclient = new WebClient();
            // we need progress changed event for progress
            webclient.DownloadProgressChanged += new DownloadProgressChangedEventHandler(DownloadProgress);
            // when calls download complated
            webclient.DownloadFileCompleted += new AsyncCompletedEventHandler(DownloadCompleted);
            // set file download url, save folder and start downlaoding
            string filedownlaodurl = "http://localhost/file.exe";
            // Anlık olarak indirilecek olan dosya ".exe"nin olduğu konuma kaydedilir
            webclient.DownloadFileAsync(new Uri(filedownlaodurl), Path.GetFileName(filedownlaodurl));
        }

        /// <summary>
        /// WebClient Download Progress Changed Event
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        /// <see cref="https://msdn.microsoft.com/en-us/library/system.net.downloadprogresschangedeventargs"/>
        private void DownloadProgress(object sender, DownloadProgressChangedEventArgs e)
        {
            // download progress
            DownlaoadProgress.Value = e.ProgressPercentage;
            // downloaded bytes
            Downloaded.Text = e.BytesReceived.ToString();
            // total bytes
            Total.Text = e.TotalBytesToReceive.ToString();
            // download percentage as string
            DownloadPercentage.Text = e.ProgressPercentage.ToString("{0}%");
        }

        /// <summary>
        /// WebClient AsyncCompleted Event Handler
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        /// <see cref="https://msdn.microsoft.com/tr-tr/library/system.componentmodel.asynccompletedeventhandler"/>
        private void DownloadCompleted(object sender, AsyncCompletedEventArgs e)
        {
            MessageBox.Show("Download completed", "Successful", MessageBoxButton.OK, MessageBoxImage.Information);
        }
    }
}