c# code 39 checksum XML S ERIA LIZA TION in Visual C#

Generator Code-39 in Visual C# XML S ERIA LIZA TION

Figure 8-2. Employee object serialized as an XML document Examine the resultant XML markup carefully. The class name (Employee) has become the name of the root element. The elements such as <EmployeeID>, <FirstName>, and <LastName> have the same name as the corresponding properties in the Employee class. Now close the application and run it again. This time click the Deserialize button. You will find that the text boxes show the property values that you specified during the last run of the application.

Imagine a case where one application is serializing objects and the other is deserializing them. What if the serialized objects contain some extra attributes and elements The application that is deserializing such objects must have some way to signal this discrepancy. Fortunately, the XmlSerializer class comes with certain events to handle such situations. These events are raised during the deserialization process when the structure of the class and the serialized XML don t match. Table 8-1 lists these events. Table 8-1. Events of the XmlSerializer Class

This event is raised when the data being deserialized contains some unexpected attribute. The event receives an event argument of type XmlAttributeEventArgs that supplies more information about the event. This event is raised when the data being deserialized contains some unexpected element. The event receives an event argument of type XmlElementEventArgs that supplies more information about the event. This event is raised when the data being deserialized contains some unexpected node. The event receives an event argument of type XmlNodeEventArgs that supplies more information about the event. This event is raised when the data being deserialized contains some recognized type that is not used or is unreferenced. The event receives an event argument of type UnreferencedObjectEventArgs that supplies more information about the event. This event applies only to SOAP-encoded XML.

To illustrate the use of these events, you need to modify the previous application as shown in Listing 8-4. Listing 8-4. Events of the XmlSerializer Class private void button2_Click(object sender, EventArgs e) { Employee emp; FileStream stream = new FileStream(Application.StartupPath + @"\employee.xml", FileMode.Open); XmlSerializer serializer = new XmlSerializer(typeof(Employee)); serializer.UnknownAttribute += new XmlAttributeEventHandler(serializer_UnknownAttribute); serializer.UnknownElement += new XmlElementEventHandler(serializer_UnknownElement); serializer.UnknownNode += new XmlNodeEventHandler(serializer_UnknownNode); emp = (Employee)serializer.Deserialize(stream); stream.Close(); textBox1.Text = emp.EmployeeID.ToString(); textBox2.Text = emp.FirstName; textBox3.Text = emp.LastName; textBox4.Text = emp.HomePhone; textBox5.Text = emp.Notes; } void serializer_UnknownNode(object sender, XmlNodeEventArgs e) { MessageBox.Show("Unknown Node " + e.Name + " found at Line " + e.LineNumber); } void serializer_UnknownElement(object sender, XmlElementEventArgs e) { MessageBox.Show("Unknown Element " + e.Element.Name + " found at Line " + e.LineNumber); } void serializer_UnknownAttribute(object sender, XmlAttributeEventArgs e) { MessageBox.Show("Unknown Attribute " + e.Attr.Name + " found at Line " + e.LineNumber); }

Notice the code marked in bold. After declaring the instance of the XmlSerializer class, it wires up three event handlers UnknownAttribute, UnknownElement, and UnknownNode that simply display a message box showing the name of the attribute, element, or node and the line number at which the attribute, element, or node is encountered. Notice how the event argument parameter is used to extract information about the unexpected content. To test these events, modify the serialized XML file manually as shown in Listing 8-5. Listing 8-5. Modifying the Serialized XML Manually < xml version="1.0" > <Employee xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" EmpCode="E001"> <EmployeeID>1</EmployeeID> <FirstName>Nancy</FirstName> <LastName>Davolio</LastName> <HomePhone>(206) 555-9857</HomePhone> <Notes>includes a BA in psychology from Colorado State University in 1970. She also completed "The Art of the Cold Call." Nancy is a member of Toastmasters International.</Notes> <OfficePhone>(206) 555-1234</OfficePhone> </Employee> Notice the markup in bold. We have added an EmpCode attribute and an <OfficePhone> element manually to the XML file. Save the file and run the application. This time when you click the Deserialize button, you will see message boxes informing you of the discrepancies. Figure 8-3 shows one such message box.