Writing/Saving XML Files - Page 1
       by kirupa  |  20 June 2007

An XML file is really nothing more than a text file with specially formatted text and funny brackets. While that oversimplified (and possibly unnecessary!) explanation makes them seem simple, writing an XML document that is properly formed is not easy without some help. Luckily, help for us comes in the form of the System.XML namespace in the .NET Framework.

The System.XML namespace provides a lot of functionality for working with XML files. One such functionality allows you to think about XML files in terms of elements and nested elements without having to worry about maintaining the XML structure like you would when writing a raw text file.

At the end of this tutorial, you will learn to write an application that produces the following XML file:

The following sections will take you through creating our above XML file gradually. Let's begin!

Creating an XmlDocument
For manipulating XML data in memory, you can use the XmlDocument class. When you create an XmlDocument object, you are creating essentially what resembles a virtual whiteboard for XML data in memory. On this whiteboard, you can fiddle around with your XML data by adding nodes, removing nodes, playing with attributes, etc.

When ready, you can write the contents from your XmlDocument object into an XML file. All of of the changes you made would be represented in the proper XML syntax in your newly saved/created file. So, let's first create our XmlDocument object. Create a new C# Console project, and inside your Main function, add the following line of code:

XmlDocument xmlDoc = new XmlDocument();

You just created a xmlDoc object of type XmlDocument. This object will store all of your XML data, and right now, your xmlDoc is now a blank file in memory. We need to populate it with some data. Let's do that now.

Adding Data
Your XML file resembles a tree with each branch and node storing some sort of information or other nodes. The name for a node that stores information is called an element, so if we want to populate our tree, we need to create a few XML element objects and add them to our XmlDocument object.

After your xmlDoc declaration, add the following line of code:

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

You are creating a new booksElement object of type XmlElement. You initialize it to the value XmlElement value returned by your xmlDoc's CreateElement method. Notice that your XmlElement is called Books.

Creating the element is not enough, though. You need to add it to your XmlDocument. You can do that by adding your booksElement as a child of xmlDoc. Add the following line of code after your booksElement line:

xmlDoc.AppendChild(booksElement);

The above line does in code what I explained in English earlier. You are adding your booksElement element as a child of your xmlDoc XmlDocument. Since this is the first element being added to your XML file, booksElement is considered to be a root element.

Your code, as of now, you should have the following three lines inside your Main method:

static void Main(string[] args)

{

XmlDocument xmlDoc = new XmlDocument();

 

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

 

xmlDoc.AppendChild(booksElement);

}

Saving the Data
We now have our XmlDocument, we created our XmlElement object, and we added that XmlElement to our XmlDocument. Now all that is left is to save our XmlDocument to disk. That is actually a lot easier than you think. Simply add the following line of code, and change the path provided to a location you want to save the file to:

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

Your XmlDocument object's Save method takes a file path as its argument. The file path you specify is where your XML file will be saved to. Don't worry if an XML file does not exist in that location, for an XML file will be created for you. In my version of the code, I am saving the data stored by my XmlDocument xmlDoc into books.xml on my desktop. Feel free to change it to whatever location you want.

If you were to run your application by pressing F5, the books.xml file be created with the Books element added. When you open your XML file, you will see an empty Books tag:

[ there isn't much to see right now in our XML file ]

Don't be alarmed if you think it is a mistake and you should be seeing more. We added only one element with the Books name, and that element didn't contain any nested elements or data. In the next page, we'll fix that by adding more information.

Onwards to the next page!

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