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How can I get a list of XML nodes by value using C#

I'm trying to get a XmlNodeList from an XmlDocument for nodes that have a certain value, with a view to removing those nodes.
XML:
<List xmlns="http://mynamespace.com/v1">
<Category>2144</Category>
<Title>My Object</Title>
<StartPrice>30.00</StartPrice>
<ReservePrice>-999</ReservePrice>
<BuyNowPrice>-999</BuyNowPrice>
</List>
Preferably I don't want to iterate through every node and check its value. I looked at trying to use LINQ from some examples but I just don't understand it enough to even attempt it.
I feel I'm getting close-ish with XPath (https://www.w3schools.com/xml/xpath_syntax.asp) but I'm beginning to think what I want to do isn't supported.
string xml = UtilityClass.SerializeObject<Listing> ( myListing);
XmlDocument xmlDocument = new XmlDocument ();
xmlDocument.LoadXml ( xml );
XmlElement root = xmlDocument.DocumentElement;
XmlNodeList nodes = root.SelectNodes ( "//*['-999']" );
Am open to other suggestions to get the same result, i.e. remove the nodes with -999 from the Xml document.
Thanks in advance

LINQ to XML is preferred API while dealing with XML in .Net Framework since 2007.
Check it out how easy to achieve what you need in one single statement.
LINQ methods are chained one after another and self-explanatory:
Get all descendants of the root node, taking into account a default namespace.
Whatever the names of the elements.
Where element value is -999.
Convert them to a List<>.
Remove those elements from the XML document.
c#
void Main()
{
XDocument xdoc = XDocument.Parse(#"<List xmlns='http://mynamespace.com/v1'>
<Category>2144</Category>
<Title>My Object</Title>
<StartPrice>30.00</StartPrice>
<ReservePrice>-999</ReservePrice>
<BuyNowPrice>-999</BuyNowPrice>
</List>");
XNamespace ns = xdoc.Root.GetDefaultNamespace();
xdoc.Descendants(ns + "List")
.Elements()
.Where(x => x.Value.Equals("-999"))
.ToList()
.ForEach(x => x.Remove());
Console.WriteLine(xdoc);
}
Output
<List xmlns="http://mynamespace.com/v1">
<Category>2144</Category>
<Title>My Object</Title>
<StartPrice>30.00</StartPrice>
</List>

Parsing Advanced XML File & Turning Information Into Class In C#

What needs to be done
Currently I have 1 Advanced XML file that needs to be parsed. I need to iterate through the file and read each "Entity" tag individually. Altough the issue I come across is reading & iterating through the Stats and Slots. Also, the amount of Stat & Slot tags will vary depending on the Entity. (Yes I have researched this topic but I still can't find a way without creating errors as I need some more guidance. The other posts haven't had the exact fix I've hoped for...)
XML File
<ROOT>
<Entity Type="Clothing" Name="Light Robe" ID="0">
<Armor>2</Armor>
<Weight>1</Weight>
<Usability>120</Usability>
<Rarity>0.1</Rarity>
<Stats>
<Stat Type="Health">10</Stat>
</Stats>
<Slots>
<Slot>Torso</Slot>
</Slots>
</Entity>
<Entity Type="Clothing" Name="Medium Robe" ID="1">
<Armor>4</Armor>
<Weight>2</Weight>
<Stats>
<Stat Type="Health">15</Stat>
</Stats>
<Usability>120</Usability>
<Rarity>0.1</Rarity>
<Slots>
<Slot>Torso</Slot>
</Slots>
</Entity>
<Entity Type="Clothing" Name="Heavy Robe" ID="2">
<Armor>6</Armor>
<Weight>4</Weight>
<Stats>
<Stat Type="Health">25</Stat>
</Stats>
<Usability>120</Usability>
<Rarity>0.1</Rarity>
<Slots>
<Slot>Torso</Slot>
</Slots>
</Entity>
</ROOT>
If anybody has any criticism of this post please say so as I'll edit accordingly.

Use XDocument for XML reading.
// Load Document
XDocument _doc = XDocument.Load("C:\\t\\My File2.txt");
// Get all Entity elements and put them into a list.
List<XElement> employees = _doc.XPathSelectElements("ROOT/Entity").ToList();
// Next you can loop thru the list to check the Entity's elements
foreach (var employee in employees)
{
// to get the armor element:
string armor = employee.Element("Armor").Value;
// to get the rarity element:
string rarity = employee.Element("Rarity").Value;
// to get the Stat element:
string stat = employee.Element("Stats").Element("Stat").Value;
// to get the Slot element:
string slot = employee.Element("Slots").Element("Slot").Value;
}
// To get one element specific by attribute use this (I check on attribute ID):
XElement emp = _doc.XPathSelectElements("ROOT/Entity").FirstOrDefault(c => c.Attribute("ID").Value == "0");
// Next you can extract information from this element just like in the foreach loop.

LINQ to XML Query to find all child values where parent element name like X C#

So lets say I have a XElement that looks something like this
<Root>
<ProductOne>
<Size>Large</Size>
<Height>2</Height>
</ProductOne>
<ProductTwo>
<Size>Small</Size>
<Type>Bar</Type>
</ProductOne>
<ProductThree>
<Size>Small</Size>
<Type>Crate</Type>
<Color>Blue</Color>
</ProductOne>
<SomeOtherStuff>
<OtherThing>CrazyData</OtherThing>
</SomeOtherStuff>
</Root>
I want to query this data and get a IEnumerable string of the child values (I.E. Size, Type, Color, and a lot of other possuble attributes) of anything that is in a element with the word "Product" in it.
So My resulting list would look like
Large
2
Small
Bar
Small
Crate
Blue
Could someone tell me how to construct such a query using LINQ?

First, you have a lot of typos with your xml. Here is the correct version:
var xml = #"
<Root>
<ProductOne>
<Size>Large</Size>
<Height>2</Height>
</ProductOne>
<ProductTwo>
<Size>Small</Size>
<Type>Bar</Type>
</ProductTwo>
<ProductThree>
<Size>Small</Size>
<Type>Crate</Type>
<Color>Blue</Color>
</ProductThree>
<SomeOtherStuff>
<OtherThing>CrazyData</OtherThing>
</SomeOtherStuff>
</Root>";
Now, here is some linq magic you can do to get the values you want.
var list = XElement.Parse(xml) //parses the xml as an XElement
.Elements() //gets all elements under the "root" node
.Where(x => x.Name.LocalName.StartsWith("Product")) // only selects elements that
// start with "product"
.SelectMany(x => x.Elements()) // inside of each of the "product" nodes, select
// all the inner nodes and flatten the results
// into a single list
.Select(x => x.Value) //select the node's inner text
.ToList(); //to list (optional)
This will give you back your wanted list as a List<string>.
Large
2
Small
Bar
Small
Crate
Blue

Can't loop children of returned XML Nodes in C#

I have a large, messy XML file and I want to retrieve ALL elements of the same name ("Item" for the sake of this post) from it, then be able to retrieve data from each element's children.
So far I have returned a list of every element called "Item" using this code, which just displays the namespace url and "Item" in p tags:
XDocument doc = XDocument.Load(#"C:\inetpub\wwwroot\mysite\myxml.xml");
XNamespace ns = "http://www.mynamespace.com";
var nodes = doc.Descendants().Elements(ns + "Item").Select(d => d.Name).ToList();
foreach(var x in nodes){
<p>#x</p>
}
However, by amending the code with the following, I can't retrieve any data of it's children and I get the error 'System.Xml.Linq.XName' does not contain a definition for 'Descendants':
foreach(var x in nodes){
<p>#x.Descendants().Element("Name")</p>
}
Here is a very basic version of my XML file:
<Item>
<Name>Item 1</Name>
<Type>Type 1</Type>
</Item>
I want to be able to search each 'Item' element for a 'Name' element and return the value. Can anyone see where I'm going wrong?

This is the problem:
.Select(d => d.Name)
You're explicitly selecting the names of the elements. If you want the actual elements (which I think you do), just get rid of that call:
var nodes = doc.Descendants().Elements(ns + "Item").ToList();
You could also get rid of the ToList() unless you need the query to be materialized eagerly.

How do I programmatically determine if an XML node is a leaf node?

I have a big XML tree like the following:
<CategoryArray>
<Category Name="Antiques" ID="20081">
<Category Name="Antiquities" ID="37903">
<Category Name="The Americas" ID="37908" />
<Category Name="Byzantine" ID="162922" />
<Category Name="Celtic" ID="162923" />
<Category Name="Egyptian" ID="37905" />
...
I'd like to iterate through all nodes to populate a control and, when doing so, check to see: is this node a leaft of a parent node? What is the easiest way to do this?

A leaf node is one that has no children so you can simply perform a check if it has children. There are various ways of doing this depending on how you're loading the XML document. For example, you can use the HasChildNodes property.
if (myXmlNode.HasChildNodes)
//is not a leaf
else
//is a leaf

Number of child nodes will give you the answer - 0 child nodes (or only text child node, depending on classes/queries you use) means it is leaf.
I.e. XElement sample form MSDN: Find a List of Child Elements
XDocument cpo = XDocument.Load("PurchaseOrders.xml");
XElement po = cpo.Root.Element("PurchaseOrder").Element("Address");
// list1 contains all children of PurchaseOrder using LINQ to XML query
IEnumerable<XElement> list1 = po.Elements();
// list2 contains all children of PurchaseOrder using XPath expression
IEnumerable<XElement> list2 = po.XPathSelectElements("./*");

I would first flatten the hierarchy - e.g. using the code from this post
How do I select recursive nested entities using LINQ to Entity
And then something like this...
using (XmlReader reader = XmlReader.Create(new StringReader(this.XML)))
{
XElement xml = XElement.Load(reader);
var all = xml.Elements("Category").Flatten(x => x.Elements("Category"));
var leafs = from cat in all
where cat.Elements("Category").Any() == false
select cat;
// or go through all...
var categories =
from cat in all
select new
{
Name = cat.Attribute("Name"),
ID = cat.Attribute("ID"),
IsLeaf = cat.Elements("Category").Any() == false,
SubCount = cat.Elements("Category").Count(),
// Subs = cat.Elements("Category").Select(x => x.Attribute("Name").ToString()).ToArray(),
};
// or put into dictionary etc.
var hash = categories.ToDictionary(x => x.Name);
}