写
XmlSerializer serializer = new XmlSerializer(typeof(PurchaseOrder));
    TextWriter writer = new StreamWriter(filename);
PurchaseOrder po=new PurchaseOrder();
serializer.Serialize(writer, po);
writer.Close();
读
XmlSerializer serializer = new XmlSerializer(typeof(PurchaseOrder));
/* If the XML document has been altered with unknown
nodes or attributes, handle them with the
UnknownNode and UnknownAttribute events.*/
serializer.UnknownNode+= new
XmlNodeEventHandler(serializer_UnknownNode);
serializer.UnknownAttribute+= new
XmlAttributeEventHandler(serializer_UnknownAttribute);
// A FileStream is needed to read the XML document.
FileStream fs = new FileStream(filename, FileMode.Open);
// Declare an object variable of the type to be deserialized.
PurchaseOrder po;
/* Use the Deserialize method to restore the object's state with
data from the XML document. */
po = (PurchaseOrder) serializer.Deserialize(fs);

protected void serializer_UnknownNode(object sender, XmlNodeEventArgs e)
{
   Console.WriteLine("Unknown Node:" +   e.Name + "\t" + e.Text);
}
protected void serializer_UnknownAttribute(object sender, XmlAttributeEventArgs e)
{
   System.Xml.XmlAttribute attr = e.Attr;
   Console.WriteLine("Unknown attribute " +
   attr.Name + "='" + attr.Value + "'");
}
可序列化的类
[XmlRootAttribute("PurchaseOrder", Namespace="http://www.cpandl.com",
IsNullable = false)]
public class PurchaseOrder
{
参考：
msdn－ XmlSerializer 类
 ms-help://MS.VSCC.2003/MS.MSDNQTR.2003FEB.2052/cpref/html/frlrfsystemxmlserializationxmlserializerclasstopic.htm