why is this only occasionally async

       private void button12_Click(object sender, EventArgs e)
        {
            BackgroundWorker worker = new BackgroundWorker();
            worker.DoWork += Worker_DoVSC;
            worker.RunWorkerAsync();
        }
   
     private void Worker_DoVSC(object sender, DoWorkEventArgs e)
        {
            Download_VSC();
        }
        private void Download_VSC()
        {
            this.BeginInvoke(new Action(() =>
            {
                label2.Text = "Downloading Visual Studio Code..."; label2.Refresh();
                this.Hide();
                dl = new WebClient();
                dl.DownloadFileCompleted += dl_DownloadFileCompleted;
                dl.DownloadProgressChanged += dl_DownloadProgressChanged;
                this.Show();
                dl.DownloadFileAsync(new Uri("https://code.visualstudio.com/sha/download?build=stable&os=win32-x64-user"), "C:\\Downloads\\VSCodeUserSetup.exe");
                sw.Start();
            }));
        }