Add items programmatically to repeatable items - asp.net

Question

How can I add an item to a repeatable property programmatically in c#:
let's say I have a node (node id 1234) and in it companies list property, where each item has comapny name and image (media picker).
how do I add an item programmtically ?
Here's what I have so far:
XPathNodeIterator xpathIterator = umbraco.library.GetXmlNodeById(NodeId.ToString());
XElement node = XElement.Parse(xpathIterator.Current.OuterXml);
var list = node.Descendants(propertyAlias).FirstOrDefault();
// how do I add items here ? something like:
list.Descendants().Add(...)
thanks.
The package I'm referring to is:
Repeatable Custom Content
update:
I think the solution is to update the xml in umbraco.config.
I have the following xml in umbraco.config:
<Companies id="1176" parentID="1447" ...>
<umbracoNaviHide>0</umbracoNaviHide>
<companyList>
<item>
<data alias="title">Company1</data>
<data alias="image" />
<data alias="text" />
<data alias="date" />
</item>
<item>
<data alias="title">Company2</data>
<data alias="image">1943</data>
<data alias="text" />
<data alias="date" />
</item>
</items>
</companyList>
</Companies>
I am able to update umbraco.config programmatically, but the results are not updated in the backend, so that when I publish the companies node again, the changes are deleted. How can I update the umbraco.config and publish the node ?
Maybe I sh should update the database directly instead ?
My code:
Document companiesDoc = new Document(COMPANIESNODEID);
XmlDocument document = content.Instance.XmlContent;
XmlNode n = document.SelectSingleNode("//Companies[#id=" + COMPANIESNODEID.ToString() + "]").SelectSingleNode("//items");
XmlNode newItem = document.CreateNode(XmlNodeType.Element, "item", null);
XmlNode dName = document.CreateNode(XmlNodeType.Element, "data", null);
XmlAttribute xn = document.CreateAttribute("alias");
xn.Value = "title";
dName.Attributes.Append(xn);
dName.InnerText = companyName;
XmlNode dImage = document.CreateNode(XmlNodeType.Element, "data", null);
XmlAttribute xi = document.CreateAttribute("alias");
xi.Value = "image";
dImage.Attributes.Append(xi);
dImage.InnerText = companyImage;
XmlNode dText = document.CreateNode(XmlNodeType.Element, "data", null);
XmlAttribute xt = document.CreateAttribute("alias");
xt.Value = "text";
dText.Attributes.Append(xt);
XmlNode dDate = document.CreateNode(XmlNodeType.Element, "data", null);
XmlAttribute xd = document.CreateAttribute("alias");
xd.Value = "date";
dDate.Attributes.Append(xd);
newItem.AppendChild(dName);
newItem.AppendChild(dImage);
newItem.AppendChild(dText);
newItem.AppendChild(dDate);
n.AppendChild(newItem);

Answer 1

I am able to update umbraco.config programmatically, but the results
are not updated in the backend, so that when I publish the companies
node again, the changes are deleted. How can I update the
umbraco.config and publish the node ?
You are going about it the wrong way. The umbraco.config file is a read-only XML representation of the Umbraco database that is generated by Umbraco and then cached. It isn't intended to be written to or accessed directly. Every time you publish a page in Umbraco this file is regenerated, hence the reasons your updates are not persisted.
You also don't want to try and write to the Umbraco database directly, either. It is very complex and requires lots of relations. Again, it isn't intended to be written to.
To update nodes directly what you really need to do is use the Umbraco Document API. This allows you direct write access to nodes which you can the programatically publish. Simple example:
Document doc = new Document(1234);
doc.getProperty("bodyText").Value = "<p>Your body text</p>";
doc.getProperty("articleDate").Value = DateTime.Now;
User author = User.GetUser(0);
doc.Publish(author);
umbraco.library.UpdateDocumentCache(doc.Id);
I'd suggest posting on http://our.umbraco.org/forum if you need more help.

Answer 2

I managed to solve the problem using this code:
var doc = new Document(COMPANIESNODEID);
XDocument xdoc = XDocument.Parse(doc.getProperty("companyList").Value.ToString());
xdoc.Element("items").Add(new XElement("item",
new XElement("data", new XAttribute("alias", "title"), companyName),
new XElement("data", new XAttribute("alias", "image"), companyImage)));
doc.getProperty("companyList").Value = xdoc.ToString();
doc.Save();
doc.Publish(new User(0));
umbraco.library.UpdateDocumentCache(doc.Id);