title: WebClient.DownloadFileAsync gets incomplete content
body: <p>I'm using <code>WebClient.DownloadFileAsync</code> to obtain a batch of files. However some files turn out to be incomplete, and there is no exception.</p>
  
  <p>My question is, how to flag when a downloaded file is not complete? There is no md5 checksum to verify.</p>
  
  <p>Code snippet is:</p>
  
  <pre><code>using (WebClient client = new WebClient())
  {
      Uri sUri = new Uri(sFileLink);
      client.DownloadFileAsync(sUri, myPath);
  }
  </code></pre>