Writing/Saving XML Files - Page 3
       by kirupa  |  20 June 2007

In the previous page, you learned how to add some nested elements. The next and final piece is adding attributes. Let's look at how to do that.

Adding Attributes
Attributes are extra information added to a node element itself. To add attribute information, copy and paste the following lines of code after your bookElement.AppendChild(authorElement) line:

XmlAttribute bookAttribute = xmlDoc.CreateAttribute("ISBN");

bookElement.SetAttributeNode(bookAttribute);

bookElement.SetAttribute("ISBN", "0553212419");

There are several steps needed to specify an attribute to a node, so let's take a look at those steps in detail.

1. Creating the Attribute
You first need to create the attribute and specify what it will be called, and we do that in our first line of code:

XmlAttribute bookAttribute = xmlDoc.CreateAttribute("ISBN");

In the above line, we create a new XmlAttribute object and use our XmlDocument object's CreateAttribute method to create our ISBN attribute.

2. Setting the Attribute to an Element
Once you have created an attribute, you need to specify which element will be using this attribute. We want our bookElement object, which references the node/element called Book, to store the ISBN information, so we can use our bookElement's SetAttributeNode value to bind our bookAttribute to our element:

bookElement.SetAttributeNode(bookAttribute);

3. Setting our Attribute Value
We have bound our attribute to an element, but we actually haven't specified what value our attribute will have. The attribute's name will be ISBN, but the name must refer to a value. We can use our bookAttribute's Value property to specify our ISBN number:

bookAttribute.Value = "0553212419";

Once you have set your attribute's value, you are set! If you run your application and examine the XML file, you will see that our first book is complete:

[ we have finished everything for one Book node ]

All of our code inside the Main method should now look like the following (with my added comments):

static void Main(string[] args)

{

XmlDocument xmlDoc = new XmlDocument();

 

//Adding the parent <Books> Element

XmlElement booksElement = xmlDoc.CreateElement("Books");

 

//Adding the <Book> Element

XmlElement bookElement = xmlDoc.CreateElement("Book");

booksElement.AppendChild(bookElement);

 

// Adding <title> and Setting Value

XmlElement titleElement = xmlDoc.CreateElement("title");

titleElement.InnerText = "Great Gatsby";

bookElement.AppendChild(titleElement);

 

// Adding <author> and Setting Value

XmlElement authorElement = xmlDoc.CreateElement("author");

authorElement.InnerText = "F. Scott Fitzgerald";

bookElement.AppendChild(authorElement);

 

// Creating Attribute and assigning it to <Book>

XmlAttribute bookAttribute = xmlDoc.CreateAttribute("ISBN");

bookElement.SetAttributeNode(bookAttribute);

bookAttribute.Value = "0553212419";

 

// Adding root element and saving file to disk

xmlDoc.AppendChild(booksElement);

xmlDoc.Save(@"C:\Users\Kirupa\Desktop\books.xml");

}

Technically, you are done, but if you remember our original XML file, we had four books that we wanted to write to our XML file. You could continue and add more lines of code such as duplicating a few more times the code you already have. While you could do that, that is (and even sounds!) tedious and unnecessary.

In the next page, I will provide a basic solution that uses methods to allow you to reuse code.

Onwards to the next page!

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