A Purchase Order Example You can cut and paste the following example code into a text file renamed with a .cs or .vb file name extension. Use the C# or Visual Basic compiler to compile the file. Then run it using the name of the executable. This example uses a simple scenario to demonstrate how an object is instantiated and serialized into a file stream using the Serialize method. The XML stream is saved to a file, and the same file is then read back and reconstructed into a copy of the original object using the Deserialize method. In this example, a class named PurchaseOrder is serialized and then deserialized. A second class named Address is also included because the public field named ShipTo must be set to an Address object. Similarly, an OrderedItem class is included because an array of OrderedItem objects must be set to the OrderedItems field. Finally, a class named Test contains the code that serializes and deserializes the classes. The CreatePO method creates the PurchaseOrder, Address, and OrderedItem class objects, and sets the public field values. The method also constructs an instance of the XmlSerializer class that is used to serialize and deserialize the PurchaseOrder object. Note that the code passes the type of the class that will be serialized to the constructor. The code also creates a FileStream that is used to write the XML stream to an XML document. The ReadPo method is a little simpler. It just creates objects to deserialize and reads out their values. As with the CreatePo method, you must first construct an XmlSerializer object, passing the type of the class to be deserialized to the constructor. Also, a FileStream is required to read the XML document. To deserialize the objects, call the Deserialize method with the FileStream as an argument. The deserialized object must be cast to an object variable of the PurchaseOrder type. The code then reads the values of the deserialized PurchaseOrder object. Note that you can also read the PO.xml file that is created to see the actual XML output. [C#] using System; using System.Xml; using System.Xml.Serialization; using System.IO; /* The XmlRootAttribute allows you to set an alternate name (PurchaseOrder) for the XML element and its namespace. By default, the XmlSerializer uses the class name. The attribute also allows you to set the XML namespace for the element. Lastly, the attribute sets the IsNullable property, which specifies whether the xsi:null attribute appears if the class instance is set to a null reference. */ [XmlRootAttribute("PurchaseOrder", Namespace="http://www.cpandl.com", IsNullable = false)] public class PurchaseOrder { public Address ShipTo; public string OrderDate; /* The XmlArrayAttribute changes the XML element name from the default of "OrderedItems" to "Items". */ [XmlArrayAttribute("Items")] public OrderedItem[] OrderedItems; public decimal SubTotal; public decimal ShipCost; public decimal TotalCost; } public class Address { /* The XmlAttribute instructs the XmlSerializer to serialize the Name field as an XML attribute instead of an XML element (the default behavior). */ [XmlAttribute] public string Name; public string Line1; /* Setting the IsNullable property to false instructs the XmlSerializer that the XML attribute will not appear if the City field is set to a null reference. */ [XmlElementAttribute(IsNullable = false)] public string City; public string State; public string Zip; } public class OrderedItem { public string ItemName; public string Description; public decimal UnitPrice; public int Quantity; public decimal LineTotal; /* Calculate is a custom method that calculates the price per item, and stores the value in a field. */ public void Calculate() { LineTotal = UnitPrice * Quantity; } } public class Test { public static void Main() { // Read and write purchase orders. Test t = new Test(); t.CreatePO("po.xml"); t.ReadPO("po.xml"); } private void CreatePO(string filename) { // Create an instance of the XmlSerializer class; // specify the type of object to serialize. XmlSerializer serializer = new XmlSerializer(typeof(PurchaseOrder)); TextWriter writer = new StreamWriter(filename); PurchaseOrder po=new PurchaseOrder(); // Create an address to ship and bill to. Address billAddress = new Address(); billAddress.Name = "Teresa Atkinson"; billAddress.Line1 = "1 Main St."; billAddress.City = "AnyTown"; billAddress.State = "WA"; billAddress.Zip = "00000"; // Set ShipTo and BillTo to the same addressee. po.ShipTo = billAddress; po.OrderDate = System.DateTime.Now.ToLongDateString(); // Create an OrderedItem object. OrderedItem i1 = new OrderedItem(); i1.ItemName = "Widget S"; i1.Description = "Small widget"; i1.UnitPrice = (decimal) 5.23; i1.Quantity = 3; i1.Calculate(); // Insert the item into the array. OrderedItem [] items = {i1}; po.OrderedItems = items; // Calculate the total cost. decimal subTotal = new decimal(); foreach(OrderedItem oi in items) { subTotal += oi.LineTotal; } po.SubTotal = subTotal; po.ShipCost = (decimal) 12.51; po.TotalCost = po.SubTotal + po.ShipCost; // Serialize the purchase order, and close the TextWriter. serializer.Serialize(writer, po); writer.Close(); } protected void ReadPO(string filename) { // Create an instance of the XmlSerializer class; // specify the type of object to be deserialized. 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); // Read the order date. Console.WriteLine ("OrderDate: " + po.OrderDate); // Read the shipping address. Address shipTo = po.ShipTo; ReadAddress(shipTo, "Ship To:"); // Read the list of ordered items. OrderedItem [] items = po.OrderedItems; Console.WriteLine("Items to be shipped:"); foreach(OrderedItem oi in items) { Console.WriteLine("\t"+ oi.ItemName + "\t" + oi.Description + "\t" + oi.UnitPrice + "\t" + oi.Quantity + "\t" + oi.LineTotal); } // Read the subtotal, shipping cost, and total cost. Console.WriteLine( "\n\t\t\t\t\t Subtotal\t" + po.SubTotal + "\n\t\t\t\t\t Shipping\t" + po.ShipCost + "\n\t\t\t\t\t Total\t\t" + po.TotalCost ); } protected void ReadAddress(Address a, string label) { // Read the fields of the Address object. Console.WriteLine(label); Console.Write("\t"+ a.Name +"\n\t" + a.Line1 +"\n\t" + a.City +"\t" + a.State +"\n\t" + a.Zip +"\n"); } 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 + "'"); } } The XML output might resemble the following: 1 Main St. AnyTown WA 00000 Wednesday, June 27, 2001 Widget S Small widget 5.23 3 15.69 15.69 12.51 28.2