Give

var doc = (from m in db.TblMapMetadata
where m.MapId == MapId
select new { XmlData = m.TWSMPMetadata }).First();

XmlDocument xml = new XmlDocument();
xml.LoadXml(doc.XmlData);

XmlNamespaceManager mgr = new XmlNamespaceManager(xml.NameTable);

mgr.AddNamespace("gco", "http://www.isotc211.org/2005/gco");

XmlNodeList nodes = xml.SelectNodes("//gco:CharacterString", mgr);

foreach (var node in nodes)
{
var n = ((XmlNode)node);
switch (n.ParentNode.Name)
{
case "organisationName":
fUnitName.InnerText = n.InnerText;
break;
case "individualName":
fUserName.InnerText = n.InnerText;
break;
case "positionName":
fUserTitle.InnerText = n.InnerText;
break;
case "voice":
fUserPhone.InnerText = n.InnerText;
break;
case "facsimile":
fUserFax.InnerText = n.InnerText;
break;
case "deliveryPoint":
fUserAddress.InnerText = n.InnerText;
break;
case "electronicMailAddress":
fUserEmail.InnerText = n.InnerText;
break;
};
}