public static string WDRetrieveCoreProperty(string docName,string propertyName)
{
   // Given a document name and a core property,retrieve the value of the property.
   // Note that because this code uses the SelectSingleNode method,// the search is case sensitive. That is,looking for "Author" is not 
   // the same as looking for "author".

   const string corePropertiesSchema = "http://schemas.openxmlformats.org/package/2006/Metadata/core-properties";
   const string dcPropertiesSchema = "http://purl.org/dc/elements/1.1/";
   const string dcTermsPropertiesSchema = "http://purl.org/dc/terms/";

   string propertyValue = string.Empty;

   using (WordprocessingDocument wdPackage = WordprocessingDocument.Open(docName,true))
   {
      // Get the core properties part (core.xml).
      CoreFilePropertiesPart corePropertiesPart = wdPackage.CoreFilePropertiesPart;

      // Manage namespaces to perform XML XPath queries.
      NaMetable nt = new NaMetable();
      XmlNamespaceManager nsManager = new XmlNamespaceManager(nt);
      nsManager.AddNamespace("cp",corePropertiesSchema);
      nsManager.AddNamespace("dc",dcPropertiesSchema);
      nsManager.AddNamespace("dcterms",dcTermsPropertiesSchema);

      // Get the properties from the package.
      XmlDocument xdoc = new XmlDocument(nt);

      // Load the XML in the part into an XmlDocument instance.
      xdoc.Load(corePropertiesPart.GetStream());

      string searchString = string.Format("//cp:coreProperties/{0}",propertyName);

      XmlNode xNode = xdoc.SelectSingleNode(searchString,nsManager);
      if (!(xNode == null))
      {
         propertyValue = xNode.InnerText;
      }
   }

   return propertyValue;
}