Recipe 17.5 Creating an XML Document Programmatically

Problem

You have data that you want to put into a more structured form, such as an XML document.

Solution

Suppose you have the following information for an address book that you want to turn into XML:

Name	Phone
Tim	999-888-0000
Newman	666-666-6666
Harold	777-555-3333

Use the XmlTextWriter to create XML for this table:

XmlTextWriter writer = new XmlTextWriter(Console.Out);
writer.Formatting = Formatting.Indented;
writer.WriteStartElement("AddressBook");
writer.WriteStartElement("Contact");
writer.WriteAttributeString("name", "Tim");
writer.WriteAttributeString("phone", "999-888-0000");
writer.WriteEndElement( );
writer.WriteStartElement("Contact");
writer.WriteAttributeString("name", "Newman");
writer.WriteAttributeString("phone", "666-666-6666");
writer.WriteEndElement( );
writer.WriteStartElement("Contact");
writer.WriteAttributeString("name", "Harold");
writer.WriteAttributeString("phone", "777-555-3333");
writer.WriteEndElement( );
writer.WriteEndElement( );
writer.Close( );

Or you can use the XmlDocument class to programmatically construct XML from other data:

public static void CreateXML( )
{
    // Start by making an XmlDocument
    XmlDocument xmlDoc = new XmlDocument( );
    // create a root node for the document
    XmlElement addrBook = xmlDoc.CreateElement("AddressBook");
    xmlDoc.AppendChild(addrBook);
    // create the Tim contact
    XmlElement contact = xmlDoc.CreateElement("Contact");
    contact.SetAttribute("name","Tim");
    contact.SetAttribute("phone","999-888-0000");
    addrBook.AppendChild(contact);
    // create the Newman contact
    contact = xmlDoc.CreateElement("Contact");
    contact.SetAttribute("name","Newman");
    contact.SetAttribute("phone","666-666-6666");
    addrBook.AppendChild(contact);
    // create the Harold contact
    contact = xmlDoc.CreateElement("Contact");
    contact.SetAttribute("name","Harold");
    contact.SetAttribute("phone","777-555-3333");
    addrBook.AppendChild(contact);

    // Display XML
    Console.WriteLine("Generated XML:\r\n{0}",addrBook.OuterXml);
    Console.WriteLine( );
}

Both of these methods generate XML that looks like this:

<AddressBook>
    <Contact name="Tim" phone="999-888-0000" />
    <Contact name="Newman" phone="666-666-6666" />
    <Contact name="Harold" phone="777-555-3333" />
</AddressBook>

Discussion

Now that you have seen two ways to do this, the question arises: "Which one to use?" The XMLDocument uses the traditional DOM method of interacting with XML, while the XmlTextReader/XmlTextWriter combination deals with XML in a streaming format. If you are dealing with larger documents, you are probably better off using the XmlTextReader/XmlTextWriter combination than the XmlDocument. The XmlTextReader/XmlTextWriter combination is the better-performing of the two when you do not need the whole document in memory. If you need the power of being able to traverse back over what you have written already, use XmlDocument.

XmlDocument is the class that implements the DOM model for XML processing in the .NET Framework. The DOM holds all of the nodes in the XML in memory at the same time, which enables tree traversal both forward and backward. DOM also allows for a writable interface to the whole XML document, which other XML classes do not provide in .NET. XmlDocument allows you to manipulate any aspect of the XML tree, is eligible to be used for XSLT transformations via the XslTransform class through its support of the IXPathNavigable interface, and allows you to run XPath queries against the document without having to create an XPathDocument first.

See Also

See the "XmlDocument Class," "XML Document Object Model (DOM)," "XslTransform Class," and "IXPathNavigable Interface" topics in the MSDN documentation.