Linq to XML Subquery

Question

I have the following XML:

<Event ID="1"..... >
    <SubEvent update="DATETIME" />
    <SubEvent update="DATETIME" />
    <SubEvent update="DATETIME" />
    <SubEvent update="DATETIME" />
    <SubEvent update="DATETIME" />
    <SubEvent update="DATETIME" />
</Event>
<Event ID="2"..... >
    <SubEvent update="DATETIME" />
    <SubEvent update="DATETIME" />
    <SubEvent update="DATETIME" />
    <SubEvent update="DATETIME" />
    <SubEvent update="DATETIME" />
    <SubEvent update="DATETIME" />
</Event>
<Event ID="3"..... >
    <SubEvent update="DATETIME" />
    <SubEvent update="DATETIME" />
    <SubEvent update="DATETIME" />
    <SubEvent update="DATETIME" />
    <SubEvent update="DATETIME" />
    <SubEvent update="DATETIME" />
</Event>

I want to remove the "Event" elements where ALL update attribute in the SubEvent are lower than the provided DATETIME.

If, for example one DATETIME is higher, the element should NOT be removed.

Answer 1

Simply select all those events and remove them from document:

DateTime date = DateTime.Now;
XDocument xdoc = XDocument.Load(path_to_xml);
xdoc.Descendants("Event")
    .Where(e => e.Elements().All(se => (DateTime)se.Attribute("update") < date))
    .Remove();
xdoc.Save(path_to_xml);

Works fine with following xml:

<?xml version="1.0" encoding="utf-8" ?>
<Events>
  <Event ID="1" >
    <SubEvent update="2013-02-05T17:06:23.8962976+03:00" />
    <SubEvent update="2013-03-08T17:06:23.8962976+03:00" />
  </Event>
  <Event ID="2">
    <SubEvent update="2013-01-05T17:06:23.8962976+03:00" />
    <SubEvent update="2013-01-05T17:06:23.8962976+03:00" />
    <SubEvent update="2013-02-05T17:06:23.8962976+03:00" />
  </Event>
  <Event ID="3">
    <SubEvent update="2013-03-05T17:06:23.8962976+03:00" />
    <SubEvent update="2013-04-05T17:06:23.8962976+03:00" />
  </Event>
</Events>

Answer 2

In suppose you're not missing a root of your xml

var xDoc = // your XDocument
var toDel = new List<XElement>();
foreach(var el in xDoc.Root.Elements("Event").Where(e => e.Elements("SubEvent").All(xel => xel.Attribute("update").Value == "DATETIME")))
{
    toDel.Add(el);
}
toDel.ForEach(e => e.Remove());

You have to replace the condition inside .All() to desirable.

Answer 3

Try this:

        var doc = XDocument.Load(@"D:\input.xml");
        var x = new List<XElement>();
        foreach (var xElement in doc.Root.Elements("Event"))
        {
            DateTime maxDt = DateTime.MinValue;

            foreach (var element in xElement.Elements("SubEvent"))
            {
                var attributeValue = element.Attributes("update").FirstOrDefault();

                if (attributeValue == null) continue;

                DateTime dt;
                if (!DateTime.TryParse(attributeValue.Value, out dt)) continue;

                if (maxDt < dt) maxDt = dt;
            }

            xElement.RemoveNodes();
            xElement.Add(new XElement("SubEvent", new XAttribute("update", maxDt.ToString("yyyy-MM-dd HH:mm:ss"))));
            x.Add(new XElement(xElement));

        }

        new XDocument(new XElement("ev", x)).Save(@"D:\output.xml");