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Count ChildElements of the same name, inside an XML Element, with XDocument

I have an XML file that looks like this -
<SST_SignageCompConfig>
<Items>
<Item>
<Index>0</Index>
<Type>1</Type>
<Duration>7</Duration>
<Name>Branding-Colours-for-business.jpg</Name>
</Item>
<Item>
<Index>1</Index>
<Type>1</Type>
<Duration>7</Duration>
<Name>Flower of Life Meditation - Copy.png</Name>
</Item>
</Items>
</SST_SignageCompConfig>
I need to count how many Item Elements there are within the Items Element.
ie how many images there are.
I'm using XDocument, so my XML file is loaded like this -
string configurationPath = System.IO.Path.Combine("C:\\SST Software\\DSS\\Compilations\\" + compName + #"\\Comp.cfg");
XDocument filedoc = XDocument.Load(configurationPath);
I've tried numerous variations of the following, with all returning a null object reference exception
foreach (var item in filedoc.Element("SST_SignageCompConfig").Element("Items").Element("Item").Nodes())
{
string name = filedoc.Element("SST_SignageCompConfig").Element("Items").Element("Item").Attribute("Name").ToString();
files.Append(name + "|");
}
I've found countless examples of how to count how many different child elements are within an element, but I need to know how many instances of the same element exist.
Can anyone point me in the right direction?

You can select all names like so:
var names = from item in filedoc.Descendants("Item")
select (string)item.Element("Name");
Or without the query syntax:
var names = filedoc.Descendants("Item").Elements("Name").Select(e => e.Value);
You can get only unique names by:
var uniqueNames = names.Distinct();

You're on the right track. Try finding out exactly which invocation is giving you the NullReferenceException. My guess is that it's the attempt to find:
.Element("SST_SignageCompConfig")
Which is your root. Try the following instead:
// note the difference between .Element and .Elements
var count = filedoc.Root.Element("Items").Elements("Item").Count();
You could also use XPath to help you nail down the navigation within your XDocument:
// returns the current top level element
var element = filedoc.Root.XPathSelectElement(".");
// If the returned element is "SST_SignageCompConfig", then:
var nextElement = filedoc.Root.XPathSelectElement("./Items")
// If the "." element is *not* "SST_SignageCompConfig", then try and locate where in your XML document that node is.
// You can navigate up with .Parent and down with .Element(s)
And so on.

How about:
var nav = fileDoc.CreateNavigator();
XPathNodeIterator navShape = nav.Select("/SST_SignageCompConfig/Items");
navShape.MoveNext()
var count = navShape.Count;

If your xml has only one Items element, this should do the trick:
filedoc.Descendants("Item")
.GroupBy(e => e.Element("Name")!=null? e.Element("Name").Value:String.Empty)
.Select(g => new
{
Name = g.Key,
Count = g.Count()
});

Because "Name" is an element and not an attribute of your xml structure.
can you try replacing this?
string name = filedoc.Element("SST_SignageCompConfig").Element("Items").Element("Item").Element("Name").ToString();

Grouping in LINQ to XML with "any" or first" aggregation

I need to group following XML using LINQ to XML or XPath by param/Type. With grouping I would like to get any (or first, doesn't matter) value of id tag.
<list>
<item>
<id>1</id>
<param>
<type>A</type>
</param>
</item>
<item>
<id>2</id>
<param>
<type>A</type>
</param>
</item>
<item>
<id>3</id>
<param>
<type>B</type>
</param>
</item>
<item>
<id>4</id>
<param>
<type>B</type>
</param>
</item>
Desirable results is
A - 1
B - 3
I've tried
var content = from item in doc.Descendants("item").Descendants("param")
group item by new
{
mType = (String)item.Element("type"),
} into g
select new
{
mType = g.Key.mType,
};
but I cannot figure out how to reference ID that is higher in hierarchy , or how to reference PARAM/TYPE when selecting ID.

I would suggest using System.Xml.Linq (XDocument)
If my understanding is good, here is what I've done:
var xml = "<list><item><id>1</id><param><type>A</type></param></item><item><id>2</id><param><type>A</type></param></item><item><id>3</id><param><type>B</type></param></item><item><id>4</id><param><type>B</type></param></item></list>";
var document = XDocument.Parse(xml);
foreach (var param in document.Root.Elements("item").GroupBy(i => i.Element("param").Element("type").Value))
{
var firstId = param.First().Element("id").Value;
Console.WriteLine ("The first of {0} = {1}", param.Key, firstId);
}
the output is :
The first of A = 1
The first of B = 3

In addition to what was suggested by Cedric, you could accomplish the same thing in pure XPath:
var xml = "<list><item><id>1</id><param><type>A</type></param></item><item><id>2</id><param><type>A</type></param></item><item><id>3</id><param><type>B</type></param></item><item><id>4</id><param><type>B</type></param></item></list>";
var document = XDocument.Parse(xml);
// start at the root, then grab the first item element which has a param/type element whose value is equal to 'B'
var answer = document.Root.XPathSelectElement("./item[./param/type='B'][1]").Element("id").Value;
In XPath, the square brackets function effectively like a where clause. My first set of square brackets qualify that I want an item that contains a matching param/type element. The second set of square brackets limit this down to the first match.

XML Xpath expression

I am trying to get the elements title and runtime (siblings) where the runtime value is larger than the input value. My C# code with the XPath expression is:
ElementValue = 140;
nodeList = root.SelectNodes(#"/moviedb/movie[./runtime>'" + ElementValue + "'/title | /moviedb/movie[./runtime>'" + ElementValue + "']/runtime");
This XPath expression is not returning anything.
My XML file:
<moviedb>
<movie>
<imdbid>tt0120689</imdbid>
<genres>Crime,Drama,Fantasy,Mystery</genres>
<languages>English,French</languages>
<country>USA</country>
<rating>8.5</rating>
<runtime>189</runtime>
<title lang="english">The Green Mile</title>
<year>1999</year>
</movie>
<movie>
<imdbid>tt0415800</imdbid>
<genres>Action,Animation,Drama,Thriller</genres>
<languages>English</languages>
<country>USA</country>
<rating>4.5</rating>
<runtime>139</runtime>
<title lang="english">Fight Club</title>
<year>2004</year>
</movie>
</moviedb>

You can instead use linq2xml
var doc=XDocument.Load(path);
var movies=doc.Elements("movie")
.Where(x=>(int)x.Element("runtime")>input)
.Select(x=>new
{
Title=x.Element("title").Value,
Runtime=(int)x.Element("runtime")
});
You can now iterate over movies
foreach(var movie in movies)
{
movie.Title;
movie.Runtime;
}

You seem to be applying the values you want off the node as a filter criteria, which won't work. I would go about this another way, first finding the nodes which meet the criteria:
nodeList = root.SelectNodes(#"/moviedb/movie[runtime > " + ElementValue + "]");
And then grabbing the child elements from each:
foreach (var node in nodeList)
{
Debug.WriteLine(node.SelectSingleNode("title").InnerText);
Debug.WriteLine(node.SelectSingleNode("runtime").InnerText);
}

You can do this using a single XPath expression by performing a union i.e. the | operator. As mentioned in other answers here, you had your select inside your predicate which would not result in the correct answer for you anyway.
Note, if you want to see if a number is bigger than another number, unless you are using a Schema driven data-type aware XQuery engine you will need to cast the text() to a number before performing the comparison. In this instance I have assumed an xs:int will be suitable for you. Also you can use the atomic gt as opposed to = which may be more efficient.
ElementValue = 140;
nodeList = root.SelectNodes(#"/moviedb/movie[xs:int(runtime) gt " + ElementValue + "]/(title | runtime)");

Linq to XML Query not picking anything

I have a rather complex XML document
<ItemSearchResponse xmlns="-------">
<OperationRequest>
<HTTPHeaders>
</HTTPHeaders>
<RequestId>0S57WGDPNC7T8HNBV76K</RequestId>
<Arguments>
</Arguments>
<RequestProcessingTime>0.441776990890503</RequestProcessingTime>
</OperationRequest>
<Items>
<Request>
<ItemSearchRequest>
</ItemSearchRequest>
</Request>
<TotalResults>1020</TotalResults>
<TotalPages>102</TotalPages>
<Item>
<ASIN>B004WL0L9S</ASIN>
<SalesRank>1</SalesRank>
<ItemAttributes>
<Manufacturer>Georgia Pacific Consumer Products LP (Cut-Sheet Paper)</Manufacturer>
<Title>GP Copy & Print Paper, 8.5 x 11 Inches Letter Size, 92 Bright White, 20 Lb, Ream of 500 Sheets (998067R)</Title>
<ItemAttributes>
</Item>
<Items>
I run this query over it and it returns of list of zero:
XDocument doc = XDocument.Load(url);
List<Item> Items = (from c in doc.Elements("Item")
select new Item
{
Title = c.Element("Title").Value
SaleRank = c.Element("SaleRank").Value
ASIN = c.Element("ASIN").Value
}).ToList<Item>();
I am really new to XLinq but according to the documentation that should work.

First of all you have not valid xml. Here is example how it should looks:
<ItemSearchResponse >
<OperationRequest>
<HTTPHeaders> </HTTPHeaders>
<RequestId>0S57WGDPNC7T8HNBV76K</RequestId>
<Arguments> </Arguments>
<RequestProcessingTime>0.441776990890503</RequestProcessingTime>
</OperationRequest>
<Items>
<Request>
<ItemSearchRequest> </ItemSearchRequest>
</Request>
<TotalResults>1020</TotalResults>
<TotalPages>102</TotalPages>
<Item>
<ASIN>B004WL0L9S</ASIN>
<SalesRank>1</SalesRank>
<ItemAttributes>
<Manufacturer>Georgia Pacific Consumer Products LP (Cut-Sheet Paper)</Manufacturer>
<Title>GP Copy & Print Paper, 8.5 x 11 Inches Letter Size, 92 Bright White, 20 Lb, Ream of 500 Sheets (998067R)</Title>
</ItemAttributes>
</Item>
</Items>
</ItemSearchResponse>
And this code works with it:
var Items = (from c in doc.Root.Element("Items").Elements("Item")
select new Item()
{
Title = c.Element("ItemAttributes").Element("Title").Value,
SaleRank = c.Element("SalesRank").Value,
ASIN = c.Element("ASIN").Value
}).ToList();
or with Descendants:
var Items = (from c in doc.Root.Descendants("Item")
select new
{
Title = c.Element("ItemAttributes").Element("Title").Value,
SaleRank = c.Element("SalesRank").Value,
ASIN = c.Element("ASIN").Value
}).ToList();

The problem lies in your use of .Elements(XName) which it seems you're assuming is recursive. It is not, It only inspects direct children of the target (in this case the document).
I believe the function you're looking for is .Descendants(XName) which will look recursively, but be warned this is not very fast on massive XML docs.

The problem is the difference between Elements and Descendants
var items = (from c in doc.Descendants("Item")
select new Item
{
Title = c.Element("ItemAttributes").Element("Title").Value,
SaleRank = c.Element("SalesRank").Value,
ASIN = c.Element("ASIN").Value
}).ToList<Item>();
Elements a list of Xml Elements directly underneath the current Element (i.e. only 1 level deep). Descendants will retrieve all elements.
Based on your Xml and your query, I showed the use of Descendant and Element. The initial loop uses Descendants(), but access to Title uses to chained Element() calls.
I tried running the code, and I'm assuming the xmlns was removed for posting, but your actual code has a real namespace in it. If not, that maybe a problem you need to resolve first.

Turns out I need to add the namespace to query.
XNamespace ns = NAMESPACE;
var items = (from c in doc.Descendants(ns +"Item")
select new Item
{
Title = c.Element(ns + "ItemAttributes").Element(ns + "Title").Value,
SalesRank = c.Element(ns +"SalesRank").Value,
ASIN = c.Element(ns + "ASIN").Value
}).ToList<Item>();

XML Lambda query in C#

I have an XmlDocument object and xml in the format:
<?xml version="1.0" encoding="utf-8"?>
<S xmlns="http://server.com/DAAPI">
<TIMESTAMP>2010-08-16 17:25:45.633</TIMESTAMP>
<MY_GROUP>
<GROUP>1 </GROUP>
<NAME>Amsterdam</NAME>
....
</MY_GROUP>
<MY_GROUP>
<GROUP>2 </GROUP>
<NAME>Ireland</NAME>
....
</MY_GROUP>
<MY_GROUP>
<GROUP>3 </GROUP>
<NAME>UK</NAME>
....
</MY_GROUP>
Using a Lambda expression (or Linq To XML if it's more appropriate) on the XmlDocument object how can i do the following:
get the text of a specific element, say the text of NAME where GROUP = 1
the value of the first occurance of the element "NAME"
Thanks a lot

Assuming you mean XDocument rather than XmlDcoument:
First question:
XNamespace ns = "http://server.com/DAAPI";
string text = (from my_group in doc.Elements(ns + "MY_GROUP")
where (int) my_group.Element(ns + "GROUP") == 1
select (string) my_group.Element(ns + "NAME")).First();
I didn't really understand the second question... what do yuo mean by "contains an element of that name"? Which name? And if you're checking for NAME being equal to a give name, wouldn't you already know that name? Did you perhaps mean the value of GROUP for a specific name? If so, it's easy:
XNamespace ns = "http://server.com/DAAPI";
int group = (from my_group in doc.Elements(ns + "MY_GROUP")
where (string) my_group.Element(ns + "NAME")
select (int) my_group.Element(ns + "GROUP")).First();
Both of these queries assume that the values do exist, and that each MY_GROUP element has a GROUP and NAME subelement. Please let us know if that's not the case.

I have used Linq to XML.
string input = "<?xml version=\"1.0\" encoding=\"utf-8\"?><S xmlns=\"http://server.com/DAAPI\"><TIMESTAMP>2010-08-16 17:25:45.633</TIMESTAMP><MY_GROUP><GROUP>1 </GROUP><NAME>Amsterdam</NAME>....</MY_GROUP><MY_GROUP><GROUP>2 </GROUP><NAME>Ireland</NAME>....</MY_GROUP><MY_GROUP><GROUP>3 </GROUP><NAME>UK</NAME>....</MY_GROUP></S>";
var doc = XDocument.Parse(input);
XNamespace ns = "http://server.com/DAAPI";
//The first question
var name = (from elem in doc.Root.Elements(ns + "MY_GROUP")
where elem.Element(ns + "GROUP") != null //Checks whether the element actually exists - if you KNOW it does then it can be removed
&& (int)elem.Element(ns + "GROUP") == 1 //This could fail if not an integer - insure it is if nessasary
select (string)elem.Element(ns + "NAME")).SingleOrDefault();

I understood only your first question. Here you are for the first:
var xmlSource = myGroup.Load(#"../../MyGroup.xml");
var q = from c in xmlSource.myGroup
where c.group = 1
select c.name;