Reading XML Element Contents using XPathDocument

/*
Reading XML Element Contents using XPathDocument
*/

using System.Xml;
using System.Xml.XPath;

private string m_xml_path;
private string m_xml_filename;

public string FilePath
{
get { return m_xml_path; }
set { m_xml_path = value; }
}

public string FileName
{
get { return m_xml_filename; }
set { m_xml_filename = value; }
}

private XPathNavigator CreateNavigator(string path, string filename)
{
XPathDocument doc = new XPathDocument(path + filename);
return doc.CreateNavigator();
}

public string GetXMLString(string xpath)
{
string xmlString = null;
try
{
XPathNavigator nav = CreateNavigator(m_xml_path, m_xml_filename);
XPathNodeIterator iter = nav.Select(xpath);
iter.MoveNext();
xmlString = iter.Current.Value;
iter = null;
nav = null;
}
catch (XPathException xe)
{
throw new XPathException(xe.Message);
}
catch (Exception ex)
{
throw new Exception(ex.Message);
}
return xmlString;
}