问为什么用GZip压缩JS和CSS会丢失数据？

EN

using (MemoryStream memoryStream = new MemoryStream(10240))
{
   //isCompressed will be true if the browser accepts gzip
   using (Stream writer = isCompressed ?
                    (Stream)(new GZipStream(memoryStream, CompressionMode.Compress)) :
                    memoryStream)
   {
      StringBuilder sb = new StringBuilder();

      //filenames is collection of multi js files need to be minify
      foreach (string fileName in fileNames)
      {
         sb.Append(File.ReadAllText(context.Server.MapPath(fileName)));
      }

      //minifier is an instance of Microsoft.Ajax.Utilities.Minifier
      string minifiedString = minifier.MinifyJavaScript(sb.ToString());

      byte[] bts = Encoding.UTF8.GetBytes(minifiedString);
      writer.Write(bts, 0, bts.Length);
   }
}