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Wednesday, November 26, 2008

LINQ to XML provides a powerful way of creating new XML data structures in a single statement referred as:

LINQ to XML provides a powerful way of creating new XML data structures in a single

statement referred to as Functional Construction.

And The main class used for this is XElement

In object oriented programming when you create object graphs, and correspondingly in W3C DOM, when creating an XML tree, you build up the XML tree in a bottom-up manner. For example using XmlDocument (the DOM implementation from Microsoft) this would be a typical way to create an XML tree.



XmlDocument doc = new XmlDocument();
XmlElement name = doc.CreateElement("name");
name.InnerText = "Patrick Hines";
XmlElement phone1 = doc.CreateElement("phone");
phone1.SetAttribute("type", "home");
phone1.InnerText = "206-555-0144";
XmlElement phone2 = doc.CreateElement("phone");
phone2.SetAttribute("type", "work");
phone2.InnerText = "425-555-0145";
XmlElement street1 = doc.CreateElement("street1");
street1.InnerText = "123 Main St";
XmlElement city = doc.CreateElement("city");
city.InnerText = "Mercer Island";
XmlElement state = doc.CreateElement("state");
state.InnerText = "WA";
XmlElement postal = doc.CreateElement("postal");
postal.InnerText = "68042";
XmlElement address = doc.CreateElement("address");
address.AppendChild(street1);
address.AppendChild(city);
address.AppendChild(state);
address.AppendChild(postal);
XmlElement contact = doc.CreateElement("contact");
contact.AppendChild(name);
contact.AppendChild(phone1);
contact.AppendChild(phone2);
contact.AppendChild(address);
XmlElement contacts = doc.CreateElement("contacts");
contacts.AppendChild(contact);
doc.AppendChild(contacts);


This style of coding provides few clues to the structure of the XML tree. LINQ to XML supports this approach to constructing an XML tree but also supports an alternative approach referred to as functional construction. Here is how you would construct the same XML tree by using LINQ to XML functional construction.


XElement contacts =
new XElement("contacts",
new XElement("contact",
new XElement("name", "Patrick Hines"),
new XElement("phone", "206-555-0144",
new XAttribute("type", "home")),
new XElement("phone", "425-555-0145",
new XAttribute("type", "work")),
new XElement("address",
new XElement("street1", "123 Main St"),
new XElement("city", "Mercer Island"),
new XElement("state", "WA"),
new XElement("postal", "68042")
)
)
);

By indenting (and squinting a bit) the code to construct the XML tree shows the structure of the underlying XML.

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