XML / XSL

<Company>
   <Address>
      ...
   </Address>
</Company>
<Customer>
   <Address>
      ...
   </Address>
</Customer>

private System.Collections.Specialized.StringCollection errors =
    new System.Collections.Specialized.StringCollection();
private System.Collections.Specialized.StringCollection warns =
    new System.Collections.Specialized.StringCollection();
public bool ValidateMapData(string strXMLDoc, string urlPath) {
    errors.Clear();
    warns.Clear();
    System.Xml.XmlTextReader tr = new System.Xml.XmlTextReader(new System.IO.StringReader(strXMLDoc));
    System.Xml.XmlValidatingReader vr = new System.Xml.XmlValidatingReader(tr);
    try {
        vr.Schemas.Add(System.Xml.Schema.XmlSchema.Read(new System.IO.StringReader(urlPath),
	    new System.Xml.Schema.ValidationEventHandler(MessageHandler)));
        vr.ValidationType = System.Xml.ValidationType.Schema;
    } catch (Exception ex) {
        while (ex != null) {
            errors.Add(ex.Message);
            ex = ex.InnerException;
        }
    }
    try {
        while(vr.Read());
    } catch (Exception ex) {
        while (ex != null) {
            errors.Add(ex.Message);
            ex = ex.InnerException;
        }
    }

    string msgs = string.Empty;
    foreach (string s in errors) {
        msgs += "\r\nError: " + s;
    }
    foreach (string s in warns) {
        msgs += "\r\nWarning: " + s;
    }
    if (errors.Count > 0) {
        msgs = "Errors validating..." + msgs;
        MessageBox.Show(this, msgs, "Schema validation", MessageBoxButtons.OK, MessageBoxIcon.Error);
    } else if (warns.Count > 0) {
        msgs = "Warnings validating..." + msgs;
        MessageBox.Show(this, msgs, "Schema validation", MessageBoxButtons.OK, MessageBoxIcon.Warning);
    } else {
        return true;
    }
    return false;
}
private void MessageHandler(object sender, System.Xml.Schema.ValidationEventArgs args) {
    if (args.Severity == System.Xml.Schema.XmlSeverityType.Error) {
        errors.Add(args.Message);
    } else {
        warns.Add(args.Message);
    }
}

MemoryStream m = new MemoryStream();
XmlDocument XmlDoc = new XmlDocument();

//Add
System.Xml.XmlTextReader reader = new XmlTextReader(m);

XmlTextWriter textWriter = new XmlTextWriter(m, System.Text.Encoding.UTF8);

// Start document
textWriter.WriteStartDocument(true);

textWriter.WriteStartElement("ns0", "HCNET_ACK_Root", "http://HoHOHo.PCNET.IB.Schema.ExternalSchema.PCNET_ACK");
textWriter.WriteStartElement("BVN");
textWriter.WriteStartElement("SendingPerson", "");
textWriter.WriteString("Terry");
textWriter.WriteEndElement();
textWriter.WriteEndElement();

// Close everything
textWriter.WriteEndElement();
textWriter.WriteEndDocument();
textWriter.Flush();
m.Position = 0;

System.IO.StreamReader sreader = new StreamReader(m);
string xml = sreader.ReadToEnd();

textWriter.Close();
reader.Close();

XmlDoc.LoadXml(xml);