CODEWITHSUNDEEP
c#listforeachlinq-to-xml
gfppaste
gfppaste

Reputation: 1121

using List.Add() method is breaking my code out of a foreach loops

So, essentially, I'm running into an interesting issue where, when the call to the "CreateXML()" function in the following code is made, an xelement is created as intended, but then, when I attempt to add it to a collection of xeleents, instead of continuing the foreach loop from which the call to "CreateXML()" originated, the foreach loop is broken out of, and a call is made to "WriteXML()". Additionally, though an XElement is created and populated, it is not added to the List. [for clarification, the foreach loops I am referring to live in the "ParseDoc()" method]

    private List<XElement> _xelemlist;
    private void WriteXml()
    {
        XElement head = new XElement("header", new XAttribute("headerattributename", "attribute"));
        foreach (XElement xelem in _xelemlist)
        {
            head.Add(xelem);
        }
        XDocument doc = new XDocument();
        doc.Add(head);

    }
    private void CreateXML(string attname, string att)
    {
        XElement xelem = new XElement("name", new XElement("child", new XAttribute(attname, att), segment));
        _xelemlist.Add(xelem);
    }
    private void ExtractSegment(HtmlNode node)
    {
        HtmlAttribute[] segatts = node.Attributes.ToArray();
        string attname = segatts[0].Value.ToString();
        string att = node.InnerText.ToString();
        CreateXML(attname, att);
    }
    private HtmlDocument ParseDoc(HtmlDocument document)
    {
        try
        {
            HtmlNode root = document.DocumentNode.FirstChild;
            foreach (HtmlNode childnode1 in root.SelectNodes(".//child1"))
            {
                foreach (HtmlNode childnode2 in node.SelectNodes(".//child2"))
                {
                    ExtractSegment(childnode2);
                }
            }
        }
        catch (Exception e) { }
        WriteXml();
        return document;
    }

When I comment out the "List.Add()" in "CreateXML()" and step through the code, the foreach loop is not broken out of after the first iteration, and the code works properly.

I have no idea what I'm doing wrong (And yes, the code is instantiated by a public member, don't worry: I am only posting the relevant internal methods to my problem)... if anyone has come across this sort of behavior before, I would really appreciate a push in the right direction to attempt to correct it... Sepcifically: is the problem just poor coding, or is this behavior a result of a property of one of the methods/libraries I am using?

One Caveat: I know that I am using HTMLAgilityPack to parse a file and extract information, but a requirement on this code forces me to use XDocument to write said information... don't ask me why.

Upvotes: 0

Views: 339

Answers (4)

Blaze Phoenix
Blaze Phoenix

Reputation: 889

Might I suggest switching to using XmlDocument?

Here is some sample code which I have written for work (changed to protect my work :D), and we are using it rather well.

Code:

XmlDocument doc = new XmlDocument();
XmlNode root;
if(File.Exists(path + "\\MyXmlFile.xml"))
{
    doc.Load(path + "\\MyXmlFile.xml");
    root = doc.SelectSingleNode("//Library");
}
else
{    
    XmlDeclaration dec = doc.CreateXmlDeclaration("1.0", "UTF-8", null);
    doc.AppendChild(dec);
    root = doc.CreateElement("Library");
    doc.AppendChild(root);
}

XmlElement book = doc.CreateElement("Book");
XmlElement title = doc.CreateElement("Title");
XmlElement author = doc.CreateElement("Author");
XmlElement isbn = doc.CreateElement("ISBN");

title.InnerText = "Title of a Book";
author.InnerText = "Some Author";
isbn.InnerText = "RandomNumbers";

book.AppendChild(title);
book.AppendChild(author);
book.AppendChild(isbn);
root.AppendChild(book);

doc.Save(path + "\\MyXmlFile.xml");

Upvotes: 0

blearn
blearn

Reputation: 1208

In your foreach loop, you are attempting to use XElement head as a list of XElements when you add() to it. This should probably be a list of XElements?

Upvotes: 0

Siva Charan
Siva Charan

Reputation: 18064

Declare the List this way,

private List<XElement> _xelemlist = new List<XElement>();

Upvotes: 0

Jon Skeet
Jon Skeet

Reputation: 1500595

I have no idea what I'm doing wrong

This, for starters:

catch (Exception e) { }

That's stopping you from seeing what on earth's going on. I strongly suspect you've got a NullReferenceException due to _xelemlist being null, but that's a secondary problem. The main problem is that by pretending everything's fine whatever happens, with no logging whatsoever, the only way of getting anywhere is by debugging, and that's an awful experience when you don't need to go through it.

It's extremely rarely a good idea catch exceptions and swallow them without any logging at all. It's almost never a good idea to do that with Exception.

Whenever you have a problem which is difficult to diagnose, improve your diagnostic capabilities first. That way, when you next run into a problem, it'll be easier to diagnose.

Upvotes: 5

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