private string GetOpfFilePath()
{
string containerXmlPath = Path.Combine(_mEpubDir, "meta-inf\\container.xml");
XmlDocument xDoc = new XmlDocument();
xDoc.Load(containerXmlPath);
XmlNode node = xDoc.SelectSingleNode("//*[@media-type = \"application/oebps-package+xml\"]");
return node != null && node.Attributes != null && node.Attributes["full-path"] != null
? Path.Combine(_mEpubDir, node.Attributes["full-path"].Value)
: String.Empty;
}