XmlDocument doc = new XmlDocument(); 
doc.Load(Server.MapPath("Authors.xml"));

Create a new element type called newElem. Call the CreateElement method of the doc type class to associate this element with the newElem type:

XmlElement newElem = doc.CreateElement("Authors");

Add the attributes to the new Authors element by creating a new XmlAttribute type for each attribute. Use the CreateAttribute method of the doc type to associate the new attribute with its corresponding attribute type. Use the Append property to add the attribute to the document.

   XmlAttribute au_id = doc.CreateAttribute("au_id");
      au_id.Value = "409-56-7009";
      newElem.Attributes.Append(au_id);
      
      XmlAttribute au_lname = doc.CreateAttribute("au_lname");
      au_lname.Value = "Smith";
      newElem.Attributes.Append(au_lname);  
      
      XmlAttribute au_fname = doc.CreateAttribute("au_fname");
      au_fname.Value = "Tom";
      newElem.Attributes.Append(au_fname); 

Create a new child element called Title using the InnerXml method. Add the title text to the element using a new type called txtNode, derived from class XmlText. Append the new element and text (or value) using the FirstChild and AppendChild properties.

   newElem.InnerXml = "<Title></Title>";
      XmlText txtNode = doc.CreateTextNode("Where Does The Time Go");
      newElem.FirstChild.AppendChild(txtNode);
      doc.DocumentElement.AppendChild(newElem);      
        
      doc.Save(Server.MapPath("Authors.xml"));

Modifying Elements and Attributes

It's no surprise the same classes which you use to add elements and attributes also handle making changes to them. This example changes an author id and title:

XmlDocument doc = new XmlDocument(); 
doc.Load(Server.MapPath("Authors.xml")); 

The SelectNodes class (derived from the Document Object Model) is used to index into the file. Each slash represents a level in the element hierarchy.

XmlNodeList nodeList = doc.SelectNodes("//Authors"); 
foreach (XmlNode node in nodeList) {

The code below checks for the author id we want to change. Once it is found, we set the value of the au_id attribute to the new author id.

if (node.Attributes["au_id"].Value == " 409-56-7009 ") {
  node.Attributes["au_id"].Value = " 409-56-7030";	     
    }

Now we check for the title we want to change. Once if is found, we use the InnerText property to make the change.

if (node.FirstChild.InnerText == " Where Does The Time Go") {
  node.FirstChild.InnerText = "Vacant Title";
    }
  }
  doc.Save(Server.MapPath("Authors.xml"));

You can see how easy it is to expand on this by adding other conditions. You can change the value of all first child elements in the document by leaving out the IF condition. You can use the ChildNodes property to flag other elements beyond the first child element.

Removing Elements and Attributes

To remove elements, the RemoveChild class is used. Using the code above, we can easily make a small change to have all title elements removed from the file.

XmlDocument doc = new XmlDocument(); 
doc.Load(Server.MapPath("Authors.xml")); 
XmlNodeList nodeList = doc.SelectNodes("//Authors"); 
 foreach (XmlNode node in nodeList) { 
                 node.RemoveChild(node.SelectSingleNode("Title"));
   }
        
doc.Save(Server.MapPath("Authors.xml"));

Again, we could expand on this by adding other conditions to flag certain elements we want removed.

Removing attributes is a little more complicated. We have to set up an attribute collection for the element using the XmlAttributeCollection class. This collection stores all of the element's attributes in a temporary array that can be indexed by name or position.

The example below uses the code above, but this time removes the au_fname attribute from each element.

XmlDocument doc = new XmlDocument(); 
doc.Load(Server.MapPath("Authors.xml")); 
XmlNodeList nodeList = doc.SelectNodes("//Authors"); 
foreach (XmlNode node in nodeList) { 

We set up an attribute collection here for each element, and find the au_name attribute and remove it by using the Remove method of the XmlAttributeCollection class.

XmlAttributeCollection attrColl = node.Attributes;
     attrColl.Remove(attrColl["au_fname"]);
  	}
      
doc.Save(Server.MapPath("Authors.xml"));

In this article, I gave you a good start in slicing-and-dicing your XML documents. Other, less common classes are also available; they can be useful depending on what you need to accomplish. There are also different ways to use the same classes to achieve the same results.

The above examples can also serve as a good template or starting point for populating XML documents from a database. By replacing the static parameters with variables from a database, you can quickly make your application XML-aware.