SAMPLE Microsoft.RuleEngine.TypedXmlDocument

 public class BREResultHelper
{
  public bool DebugTrace(string value)
  {
    System.Diagnostics.Debug.WriteLine("<" + value + ">");
    return true;
  }

  public void AddValidationError(TypedXmlDocument resultMessage, string rule, string message)
  {
    var node = GetNode(resultMessage.Document.OwnerDocument, "//ns0:BREResult/BrokenRules");
    AddNode(node, "BrokenRule");
    AddNode(node.LastChild, "Rule", rule);
    AddNode(node.LastChild, "Message", message);
  }

  public void AddSetting(TypedXmlDocument resultMessage, string key, string value)
  {
    var node = GetNode(resultMessage.Document.OwnerDocument, "//ns0:BREResult/Settings");
    AddNode(node, "Setting");
    AddNode(node.LastChild, "Key", key);
    AddNode(node.LastChild, "Value", value);
  }

  private void AddNode(XmlNode node, string elementName)
  {
    XmlElement newElement = node.OwnerDocument.CreateElement(elementName);
    node.AppendChild(newElement);
  }

  private void AddNode(XmlNode node, string elementName, string value)
  {
    XmlElement newElement = node.OwnerDocument.CreateElement(elementName);
    XmlText elementText = node.OwnerDocument.CreateTextNode(value);
    node.AppendChild(newElement);
    node.LastChild.AppendChild(elementText);
  }

  private XmlNode GetNode(XmlDocument doc, string xpath)
  {
    XmlNamespaceManager xmlnsManager = new XmlNamespaceManager(doc.NameTable);
    xmlnsManager.AddNamespace("ns0", "http://xyz.BizTalk.ESB.Schemas.BREResult");
    return doc.SelectSingleNode(xpath, xmlnsManager);
  }
}


public void AddValidationError(TypedXmlDocument resultMessage, string rule, string message)
 {
  XNamespace ns = "http://xyz.BizTalk.ESB.Schemas.BREResult";
  XDocument doc = XDocument.Parse(resultMessage.Document.InnerXml);
  XElement root = doc.Element(ns + "BREResult").Element("BrokenRules");
  root.Add(new XElement("BrokenRule",
    new XElement("Rule", rule),
    new XElement("Message", message)));

  resultMessage.Document.InnerXml = doc.ToXmlDocument().InnerXml;
 }