System.Net.WebClient.DownloadDataTaskAsync C# (CSharp) Method

        public System.Threading.Tasks.Task<byte[]> DownloadDataTaskAsync(System.Uri address) { throw null; }
        public void DownloadFile(string address, string fileName) { }

        public static async Task BeginDownloadMinecraft(this MainWindow window)
        {
            window.LoadingBox.Visibility = Visibility.Visible;
            window.LoadingText.Content = "Updating Minecraft...";
            window.LoadingProgress.IsIndeterminate = true;
            if (!Directory.Exists(Globals.LauncherDataPath + @"\Minecraft")) Directory.CreateDirectory(Globals.LauncherDataPath + @"\Minecraft");
            if (!Directory.Exists(Globals.LauncherDataPath + @"\Minecraft\bin")) Directory.CreateDirectory(Globals.LauncherDataPath + @"\Minecraft\bin");
            if (!Directory.Exists(Globals.LauncherDataPath + @"\Minecraft\bin\natives")) Directory.CreateDirectory(Globals.LauncherDataPath + @"\Minecraft\bin\natives");
            WebClient c = new WebClient();
            try
            {
                
                if ((long)Settings.Default["CachedLWJGLTimestamp"] == null || LauncherInformation.Current.LWJGLTimestamp > (long)Settings.Default["CachedLWJGLTimestamp"])
                {
                    window.LoadingText.Content = "Downloading updated LWJGL...";
                    byte[] d = await c.DownloadDataTaskAsync(LauncherInformation.Current.LWJGLLocation);
                    
                    ZipFile f = ZipFile.Read(new MemoryStream(d));
                    f.ExtractAll(Globals.LauncherDataPath + @"\Minecraft\bin", ExtractExistingFileAction.OverwriteSilently);

                    Settings.Default["CachedLWJGLTimestamp"] = LauncherInformation.Current.LWJGLTimestamp;
                    Settings.Default.Save();
                }
                if((long)Settings.Default["CachedMinecraftTimestamp"] == null || LauncherInformation.Current.MinecraftTimestamp > (long)Settings.Default["CachedMinecraftTimestamp"])
                {
                    MessageBoxResult r = MessageBox.Show("Do you want to update Minecraft? (Latest version: " + LauncherInformation.Current.MinecraftVersion + ")", "MCLauncher", MessageBoxButton.YesNo, MessageBoxImage.Question);

                    if (r == MessageBoxResult.Yes)
                    {
                        window.LoadingText.Content = "Downloading Minecraft " + LauncherInformation.Current.MinecraftVersion + "...";
                        byte[] mc = await c.DownloadDataTaskAsync(LauncherInformation.Current.MinecraftLocation);

                        File.WriteAllBytes(Globals.LauncherDataPath + @"\Minecraft\bin\minecraft.jar", mc);
                        Settings.Default["CachedMinecraftTimestamp"] = LauncherInformation.Current.MinecraftTimestamp;
                        Settings.Default.Save();
                    }
                }
            }
            catch (WebException ex)
            {
                MessageBox.Show("Failed to update Minecraft. Is your internet down? Exception information: " + ex.ToString(), "An error has occured.", MessageBoxButton.OK, MessageBoxImage.Error);
            }
            finally
            {
                c.Dispose();
            }
            
        }