Develop Reference

Conditional Output by Linq to XML

Below is the sample XML that I am trying to read using Linq to XML:
<root>
<Employee>
<Name>Jeff</Name>
<Department>Account</Department>
</Employee>
<Employee>
<Name>David</Name>
<Department>Finance</Department>
</Employee>
<Employee>
<Name>Neil</Name>
<Department>Sales</Department>
</Employee>
<Employee>
<Name>Jason</Name>
<Department>Retail</Department>
</Employee>
</root>
Now, I need to select Employee elements which are from "Account" Department. If there are none in Account then I need to pick Employee element from Finance.
How can I do that?

As an option you can use this code:
var result = XElement.Parse(xml).Descendants("Employee")
.GroupBy(x => x.Element("Department").Value)
.OrderByDescending(x=>x.Key=="Account")
.FirstOrDefault(x => (x.Key == "Account" && x.Count() > 0) ||
x.Key == "Finance").ToList();

You can do this, it is not the most elegant way. Just use || and take FirstOrDefault
var result = doc.Root.Descendants("Employee").
Where(x => x.Element("Department").Value == "Account" || x.Element("Department").Value == "Finance").
FirstOrDefault();

Combining Linq and XPath you can do it like this:
var document = XDocument.Load("data.xml").Root;
//Find a Department with a given value and retrieve its Employee parent
string xPath = "//Department[text() = '{0}']/parent::Employee";
//Search for "Account" Department. If nun was found will return null and then
//search for "Finance"
var employee = document.XPathSelectElement(string.Format(xPath, "Account")) ??
document.XPathSelectElement(string.Format(xPath, "Finance"));
If you do not want to use XPath then you can do this:
var employee = (from item in XDocument.Load("data.xml").Descendants("Employee")
let department = item.Element("Department").Value
orderby department == "Account" ? 1 :
department == "Finance" ? 2 : 3
select item).FirstOrDefault();
For all employees of those departments:
var employee = (from item in XDocument.Load("data.xml").Descendants("Employee")
group item by item.Element("Department").Value into grouping
orderby grouping.Key == "Account" ? 1 :
grouping.Key == "Finance" ? 2 : 3
select grouping.ToList()).FirstOrDefault();

XML query - retrieving values

To my great frustration, I spent half a day to build some queries for an XML document and I don't know anything more than I knew before I started. So, I'm taking the easy way out and ask again for help.
The XML code is like this:
<?xml version="1.0" ?>
<Main>
<alpha Id = "AlphaId_1">
<beta>AlphaId1_Beta</beta>
<gamma>AlphaId1_Gama</gamma>
<delta Type = "A">AlphaId1_DeltaTypeA</delta>
<delta Type = "B">AlphaId1_DeltaTypeB</delta>
<kapa Id="01">
<description>AlphaId1_KapaId1_Descr</description>
<name>AlphaId1KapaId1_Name</name>
<teta>AlphaId1KapaId1_Teta</teta>
</kapa>
<kapa Id="02">
<description>AlphaId1KapaId2_Descr</description>
<name>AlphaId1KapaId2_Name</name>
<teta>AlhaId1KapaId2_Teta</teta>
</kapa>
</alpha>
<alpha Id = "AlphaId_2">
<beta>AlphaId2_Beta</beta>
<gamma>AlphaId2_Gama</gamma>
<delta Type = "A">AlphaId2_DeltaTypeA</delta>
<delta Type = "B">AlphaId2_DeltaTypeB</delta>
<kapa Id="01">
<description>AlphaId2_KapaId1_Descr</description>
<name>AlphaId2KapaId2_Name</name>
<teta>AlphaId2KapaId2_Teta</teta>
</kapa>
<kapa Id="02">
<description>AlphaId1KapaId2_Descr</description>
<name>AlphaId2KapaId2_Name</name>
<teta>AlhaId2KapaId2_Teta</teta>
</kapa>
</alpha>
</Main>
I am looking for a query to retrieve for example the value "AlphaId2_DeltaTypeA".
The second query should retrieve all the description values from every KapaId for a selected AlphaId.
The only code I could come up with is
XDocument xdoc = XDocument.Load(#"doc.xml");
IEnumerable<XElement> list1 = xdoc.Root.Descendants("delta");
var cifmi =
from el in list1
where (string)el.Attribute("Type") == "A"
select el;
foreach (XElement el in cifmi)
{
textBox1.AppendText(el.Value + System.Environment.NewLine);
}
The code finds two values instead of one.

var xDoc = XDocument.Load("Input.txt");
var alpha = (from a in xDoc.Root.Elements("alpha")
let deltas = a.Elements("delta")
let deltaA = deltas.First(x => (string)x.Attribute("Type") == "A")
where (string)deltaA == "AlphaId2_DeltaTypeA"
select a).First();
var descriptions = alpha.Elements("kapa")
.Select(x => (string)x.Element("description")).ToList();
It will only look for <delta> which has both Type="A" and value of AlphaId2_DeltaTypeA. If you only care about value try that one:
var alpha = (from a in xDoc.Root.Elements("alpha")
let deltas = a.Elements("delta")
where deltas.Any(x => (string)x == "AlphaId2_DeltaTypeA")
select a).First();
Update
*alpha Id == "AlphaId_1" and delta Type = "A" and the answer is AlphaId1_DeltaTypeA*
var alpha = (string)xDoc.Root
.Elements("alpha")
.First(x => (string)x.Attribute("Id") == "AlphaId_1")
.Elements("delta")
.First(x => (string)x.Attribute("Type") == "A");

Iterating through in LinqToXml query

As I haven't work yet with LinqToXml I'd like to ask you for help
Source XML:
<Projects xmlns="">
<Project id="12345">
<Name>AName</Name>
</Project>
<Project id="23456">
<Name>BName</Name>
</Project>
</Projects>
Linq query:
var q = (from xe in datasource.Descendants()
select new Data{
ID = xe.Name.ToString(),
Name = xe.Value.ToString()
}).ToList();
Output:
Project AName
Name AName
Project BName
Name BName
Desired output:
12345 AName
23456 BName
So it seems that query is iterating through all descendants and takes Name as Node Name and Value as Node value. How should I modify it to get desired output?
How about something like this:
Get all <Name> nodes for iteration
select Value of that node and id attribute for ancestor
P.S. Do you recommend any particular tutorials for LinqToXml?

var q = (from p in datasource.Descendants("Project")
select new Data {
ID = (string)p.Attribute("id"),
Name = (string)p.Element("Name")
}).ToList();
Consider also to have ID property of integer type, then you will be able to parse it this way:
ID = (int)p.Attribute("id")
Also you can use methods (fluent) syntax:
var q = datasource
.Descendants("Project")
.Select(p => new Data {
ID = (string)p.Attribute("id"),
Name = (string)p.Element("Name") })
.ToList();

Reorder using Join in Linq

I want my XElements in document order.
Can I reorder my xpathGroups using Join like in this example?
XDocument message_doc = XDocument.Load(message);
var xpathGroups =
from e in contextErrors
group e by SelectElement(message_doc, e.XPath) into g
select new
{
Element = g.Key,
ErrorItems = g,
};
var documentOrderedGroups =
from elem in message_doc.Root.DescendantsAndSelf()
join e in xpathGroups on elem equals e.Element
select e;
Message:
<root>
<a>
<aa>
<aaa>9999</aaa>
</aa>
<aa>
<aaa>8888</aaa>
</aa>
</a>
<b>
<bb>
<bbb>7777</bbb>
</bb>
</b>
<c>
<cc>
<ccc>6666</ccc>
</cc>
</c>
</root>
Input data:
/root/c[1]/cc[1]/ccc[1]
/root/a[1]/aa[2]/aaa[1]
/root/b[1]/bb[1]/bbb[1]
/root/a[1]/aa[1]/aaa[1]
Expected result:
/root/a[1]/aa[1]/aaa[1]
/root/a[1]/aa[2]/aaa[1]
/root/b[1]/bb[1]/bbb[1]
/root/c[1]/cc[1]/ccc[1]

Your original queries work, and the result is an object with the element and its relevant XPath query in document order. However, the result conflicts with the comment you made that you only want the elements in document order.
Elements and XPath: if you want both the element and its XPath then the join will remain as part of the query but I would replace the grouping with a projection into an anonymous type.
var xpathElements = contextErrors.Select(e => new
{
Element = message_doc.XPathSelectElement(e.XPath),
XPath = e.XPath
});
var ordered = from e in message_doc.Descendants()
join o in xpathElements on e equals o.Element
select o;
Elements only: if you only want the elements to be in document order, the following approach would work as well.
var xpathElements = contextErrors.Select(e => message_doc.XPathSelectElement(e.XPath));
var ordered = message_doc.Descendants()
.Where(e => xpathElements.Any(o => e == o));
In both examples I've used the XPathSelectElement method to take the place of your
SelectElement method, which I gather has the same purpose.

query xmlnode using linq

I have following file:
<root>
<Product desc="Household">
<Product1 desc="Cheap">
<Producta desc="Cheap Item 1" category="Cooking" />
<Productb desc="Cheap Item 2" category="Gardening" />
</Product1>
<Product2 desc="Costly">
<Producta desc="Costly Item 1" category="Decoration"/>
<Productb desc="Costly Item 2" category="Furnishing" />
<Productc desc="Costly Item 3" category="Pool" />
</Product2>
</Product>
</root>
I want to find out info like: Total items in Cheap and Costly,
list of all category (like Cooking, Gardening, DEcoration...), list of sorted category and select only the Product which is 'Costly'
How can i do using LINQ.
I did this till now:
XElement xe = XElement.Load(Server.MapPath("~/product.xml"));
????

Your XML structure is unfortunate as it uses a Product element for three levels of the hierarchy. Do you have other elements similar to the "household" one?
Assuming we only want the household ones, you can use:
Count items in each of cheap/costly
xe.Element("Product") // Select the Product desc="household" element
.Elements() // Select the elements below it
.Select(element => new { Name=(string) element.Attribute("desc"),
Count=element.Elements().Count() });
List all categories
xe.Descendants() // Select all descendant elements
.Attributes() // All attributes from all elements
// Limit it to "category" elements
.Where(attr => attr.Name == "category")
// Select the value
.Select(attr => attr.Value)
// Remove duplicates
.Distinct();
To sort this, just use .OrderBy(x => x) at the end.
Select 'costly' products
xe.Descendants() // Select all elements
// Only consider those with a "Costly" description
.Where(element => (string) element.Attribute("desc") == "Costly")
// Select the subelements of that element, and flatten the result
.SelectMany(element => element.Elements());

Well, personally I find it easier with XmlDocument:
XmlDocument root = new XmlDocument();
root.LoadXml(xml); // or .Load(path);
var categories = root.SelectNodes(
"/root/Product/Product/Product/#category")
.Cast<XmlNode>().Select(cat => cat.InnerText).Distinct();
var sortedCategories = categories.OrderBy(cat => cat);
foreach (var category in sortedCategories)
{
Console.WriteLine(category);
}
var totalItems = root.SelectNodes(
"/root/Products/Product/Product").Count;
Console.WriteLine(totalItems);
foreach (XmlElement prod in root.SelectNodes(
"/root/Product/Product[#desc='Costly']/Product"))
{
Console.WriteLine(prod.GetAttribute("desc"));
}