ICSharpCode.SharpZipLib.Zip.ZipException: EOF in header

//异常提示：ICSharpCode.SharpZipLib.Zip.ZipException: EOF in header 

NPOIMemoryStream stream = new NPOIMemoryStream();
using (var fileStream = File.Open(filePath, FileMode.Open, FileAccess.ReadWrite))
{
    fileStream.CopyTo(stream);
    stream.Position = 0; //这一句不加就会上面的异常错误
}
IWorkbook wk = new NPOI.XSSF.UserModel.XSSFWorkbook(stream);