I have a XML like this:
<?xml version="1.0" encoding="utf-8"?>
<Document>
<Interface>
<Sections xmlns="http://www.siemens.com/automation/Openness/SW/Interface/v4">
<Section Name="Static">
<Member Name="3bool1" Datatype=""3bool"" Remanence="NonRetain" Accessibility="Public">
<AttributeList>
<BooleanAttribute Name="ExternalAccessible" SystemDefined="true">true</BooleanAttribute>
<BooleanAttribute Name="ExternalVisible" SystemDefined="true">true</BooleanAttribute>
<BooleanAttribute Name="ExternalWritable" SystemDefined="true">true</BooleanAttribute>
<BooleanAttribute Name="SetPoint" SystemDefined="true">false</BooleanAttribute>
</AttributeList>
<Sections>
<Section Name="None">
<Member Name="bool1" Datatype="Bool" />
<Member Name="bool2" Datatype="Bool" />
<Member Name="bool3" Datatype="Bool" />
</Section>
</Sections>
</Member>
<Member Name="int7" Datatype="Int" Remanence="NonRetain" Accessibility="Public">
<AttributeList>
<BooleanAttribute Name="ExternalAccessible" SystemDefined="true">true</BooleanAttribute>
<BooleanAttribute Name="ExternalVisible" SystemDefined="true">true</BooleanAttribute>
<BooleanAttribute Name="ExternalWritable" SystemDefined="true">true</BooleanAttribute>
<BooleanAttribute Name="SetPoint" SystemDefined="true">true</BooleanAttribute>
</AttributeList>
</Member>
</Section>
</Sections>
</Interface>
</Document>
With the following code I can take all the descendants "Member" elements of bool "Datatype":
XNamespace ns = "http://www.siemens.com/automation/Openness/SW/Interface/v4";
var memb = doc.Descendants(ns + "Member")
.Select(f => f.Attribute("Datatype"))
.Where(n => n.Value.Contains("Bool"))
.ToList();
memb.ForEach(i => Console.WriteLine("{0}\t", i));
What I want to do is:
You have an XDocument with a recursive schema in which <Member> descendants contain nested <Member> descendants. You would like to iterate through the document, returning top-level <Member> elements grouped with their topmost <Member> descendants, then extract some data from those descendants. Currently you are using XDocument.Descendants() to iterate through the document, which doesn't do a good job of conveniently capturing the grouping of parents and children.
One way to do this would be to use the method XElementExtensions.DescendantsUntil(this XElement root, Func<XElement, bool> predicate, bool includeSelf) from this answer to How to find highest level descendants with a given name to find the topmost <Member> elements, then for each of those, use DescendantsUntil() again to find their topmost <Member> descendants.
First define DescendantsUntil() as follows:
public static partial class XElementExtensions
{
/// <summary>
/// Enumerates through all descendants of the given element, returning the topmost elements that match the given predicate
/// </summary>
/// <param name="root"></param>
/// <param name="filter"></param>
/// <returns></returns>
public static IEnumerable<XElement> DescendantsUntil(this XElement? root, Func<XElement, bool> predicate)
{
if (predicate == null)
throw new ArgumentNullException(nameof(predicate));
return GetDescendantsUntil(root, predicate, false);
}
static IEnumerable<XElement> GetDescendantsUntil(XElement? root, Func<XElement, bool> predicate, bool includeSelf)
{
if (root == null)
yield break;
if (includeSelf && predicate(root))
{
yield return root;
yield break;
}
var current = root.FirstChild<XElement>();
while (current != null)
{
var isMatch = predicate(current);
if (isMatch)
yield return current;
// If not a match, get the first child of the current element.
var next = (isMatch ? null : current.FirstChild<XElement>());
if (next == null)
// If no first child, get the next sibling of the current element.
next = current.NextSibling<XElement>();
// If no more siblings, crawl up the list of parents until hitting the root, getting the next sibling of the lowest parent that has more siblings.
if (next == null)
{
for (var parent = current.Parent as XElement; parent != null && parent != root && next == null; parent = parent.Parent as XElement)
{
next = parent.NextSibling<XElement>();
}
}
current = next;
}
}
public static TNode? FirstChild<TNode>(this XNode node) where TNode : XNode => node switch
{
XContainer container => container.FirstNode?.NextSibling<TNode>(true),
_ => null,
};
public static TNode? NextSibling<TNode>(this XNode node) where TNode : XNode =>
node.NextSibling<TNode>(false);
public static TNode? NextSibling<TNode>(this XNode node, bool includeSelf) where TNode : XNode
{
for (var current = (includeSelf ? node : node.NextNode); current != null; current = current.NextNode)
{
var nextTNode = current as TNode;
if (nextTNode != null)
return nextTNode;
}
return null;
}
//Taken from this answer https://stackoverflow.com/a/46016931/3744182
//To https://stackoverflow.com/questions/46007738/how-to-find-first-descendant-level
//With added nullability annotations and updated syntax
}
And now you can do:
XNamespace ns = "http://www.siemens.com/automation/Openness/SW/Interface/v4";
XName name = ns + "Member";
var members = doc
.Root.DescendantsUntil(e => e.Name == name)
.Select(e => (Parent: e, Children : e.DescendantsUntil(c => c.Name == name).ToList()))
//.Where(i => i.Children.Count > 0) // Uncomment to filter out <Member> elements with no child members.
.ToList();
members.ForEach(i => Console.WriteLine("Parent: \"{0}\", Children: {1}",
i.Parent.Attribute("Name")?.Value,
i.Children.Count == 0
? "None" :
string.Join(",",
i.Children.Select(c => $"\"{c.Attribute("Name")?.Value}\""))));
Which prints
Parent: "3bool1", Children: "bool1","bool2","bool3"
Parent: "int7", Children: None
If you are not interested in the <Member Name="int7" element which has no <Member> children, you may filter such elements out by uncommenting the Where() clause above:
.Where(i => i.Children.Count > 0) // Uncomment to filter out <Member> elements with no child members.
Demo fiddle here.