Question

I’m a LAMP guy and ended up working this small news module for an asp.net site, which I am having some difficulty with. I basically am adding and deleting elements via AJAX based on the id. Before, I had it working based on the the index of a set of elements, but would have issues deleting, since the index would change in the xml file and not on the page (since I am using ajax).

Here is the rundown

news.xml

<?xml version="1.0" encoding="utf-8"?>
<news>
  <article id="1">
    <title>Red Shield Environmental implements the PARCSuite system</title>
    <story>Add stuff here</story>
  </article>
  <article id="2">
    <title>Catalyst Paper selects PARCSuite for its Mill-Wide Process...</title>
    <story>Add stuff here</story>
  </article>
  <article id="3">
    <title>Weyerhaeuser uses Capstone Technology to provide Control...</title>
    <story>Add stuff here</story>
  </article>
</news>

Page sending del request:

<script type="text/javascript">
        $(document).ready(function () {
            $('.del').click(function () {
                var obj = $(this);
                var id = obj.attr('rel');
                $.post('add-news-item.aspx',
                    { id: id },
                    function () {
                        obj.parent().next().remove();
                        obj.parent().remove();
                    }
                );
            });
        });
    </script>
    <a class="del" rel="1">...</a>
    <a class="del" rel="1">...</a>
    <a class="del" rel="1">...</a>

My functions

protected void addEntry(string title, string story)
    {
        XmlDocument news = new XmlDocument();
        news.Load(Server.MapPath("../news.xml"));

        XmlAttributeCollection ids = news.Attributes;
        //Create a new node
        XmlElement newelement = news.CreateElement("article");
        XmlElement xmlTitle = news.CreateElement("title");
        XmlElement xmlStory = news.CreateElement("story");

        XmlAttribute id = ids[0];
        int myId = int.Parse(id.Value + 1);
        id.Value = ""+myId;
        newelement.SetAttributeNode(id);
        xmlTitle.InnerText = this.TitleBox.Text.Trim();
        xmlStory.InnerText = this.StoryBox.Text.Trim();


        newelement.AppendChild(xmlTitle);
        newelement.AppendChild(xmlStory);

        news.DocumentElement.AppendChild(newelement);

        news.Save(Server.MapPath("../news.xml"));
    }

    protected void deleteEntry(int selectIndex)
    {
        XmlDocument news = new XmlDocument();
        news.Load(Server.MapPath("../news.xml"));

        XmlNode xmlnode = news.DocumentElement.ChildNodes.Item(selectIndex);
        xmlnode.ParentNode.RemoveChild(xmlnode);
        news.Save(Server.MapPath("../news.xml"));
    }

I haven’t updated deleteEntry() and you can see, I was using the array index but need to delete the article element based on the article id being passed. And when adding an entry, I need to set the id to the last elements id + 1. Yes, I know SQL would be 100 times easier, but I don’t have access so… help?

Answer 1

Linq to XML should make this a lot simpler. Here would be the equivalent of what you are trying:

        public void AddEntry(string title, string story)
        {
            var newElement = new XElement("article", new XElement("title", title), new XElement("story", story));                
            XDocument doc = XDocument.Parse(testXml);
            var maxId = doc.Descendants("article").Attributes("id").Max(x => int.Parse(x.Value));
            newElement.Add(new XAttribute("id", ++maxId));
            doc.Descendants("news").First().Add(newElement);
            //save the document
        }

        public void DeleteEntry(int selectIndex)
        {
            XDocument doc = XDocument.Parse(testXml);
            doc.Descendants("article").Where(x => int.Parse(x.Attribute("id").Value) == selectIndex).Remove();
            //save the document
        }

Based on the size of your xml file and the number of requests, you may want to look into other approaches than loading the document, and saving it for each call to add and delete.

EDIT: Note that you would need to add null checks to the above code…