Applied XML Programming for Microsoft .NET.pdf - Csbdu.in

XmlAttributeOverrides object to override the serialization attributes set on the class.The XmlAttributeOverrides class is a collection and contains pairs consisting of theobject types that will be overridden and the changes to apply.As shown in the following code, you first create an instance of the XmlAttributes class—that is, a helper class that contains all the pairs of overriding objects. Next you createan attribute object that is appropriate for the object being overridden. For example,create an XmlElementAttribute object to override a property. In doing so, you canoptionally change the element name or the namespace. Then store the override in theXmlAttributes object. Finally, add the XmlAttributes object to the XmlAttributeOverridesobject and indicate the element to which all those overrides will apply.// Create the worker collection of changesXmlAttributes changes = new XmlAttributes();// Add the first override (change the element's name)XmlElementAttribute newElem = new XmlElementAttribute();newElem.ElementName = "New name";changes.XmlElements.Add(newElem);// Create the list of overridesXmlAttributeOverrides over = new XmlAttributeOverrides();// Fill the overrides list (Employee is the target class)over.Add(typeof(Employee), "Element-to-Override", changes);The instance of the XmlAttributeOverrides class is associated with the XML serializer atcreation time, as shown here:XmlSerializer ser = new XmlSerializer(typeof(Employee), over);NoteAttribute overriding also enables you to use derived classes in lieuof the defined classes. For example, suppose you have a propertyof a certain type. To force the serializer (both in serialization anddeserialization) to use a derived class, follow the steps outlined inthe preceding code but also set the Type property on the overridingelement, as shown here:// Manager is a class that inherits from EmployeenewElem.Type = typeof(Manager);Attribute overriding is a useful technique, and in the next section, we'll see it in action.Mapping SQL Server Data to ClassesIn Chapter 8, we saw the ExecuteXmlReader method exposed by the SqlCommandclass in the SQL Server–managed provider. The ExecuteXmlReader method executesa command against the database and returns an XML reader if the output of thecommand can be expressed as a well-formed XML document or fragment. Let's seewhat's needed to transform that output into an instance of a class. The following code isat the heart of the example. You call into a method, the method executes an SQL XML411