Download file and automatically save it to folder

I'm trying to make a UI for downloading files from my site. The site have zip-files and these need to be downloaded to the directory entered by the user. However, I can't succeed to download the file, it just opens up from a temporary folder.

Code:

private void webBrowser1_Navigating(object sender, WebBrowserNavigatingEventArgs e)
{
        e.Cancel = true;
        string filepath = null;
            filepath = textBox1.Text;
            WebClient client = new WebClient();
            client.DownloadFileCompleted += new AsyncCompletedEventHandler(client_DownloadFileCompleted);
            client.DownloadFileAsync(e.Url, filepath);
}

Full sourcecode: http://en.paidpaste.com/LqEmiQ