Develop Reference

how can i get node Element value From LINQ?

i have a collection of service users, i want to iterate over ServiceUsers and extract value from ServiceUser, (ID, USER_NAME, UN_ID, IP, NAME)
<ServiceUsers xmlns="">
<ServiceUser>
<ID>280334</ID>
<USER_NAME>YVELAMGAMOIYENET12:206322102</USER_NAME>
<UN_ID>731937</UN_ID>
<IP>91.151.136.178</IP>
<NAME>?????????????????????: 123456</NAME>
</ServiceUser>
<ServiceUser>
<ID>266070</ID>
<USER_NAME>ACHIBALANCE:206322102</USER_NAME>
<UN_ID>731937</UN_ID>
<IP>185.139.56.37</IP>
<NAME>123456</NAME>
</ServiceUser>
</ServiceUsers>
my Code looks like this, but i am getting null point exception.
XDocument doc = XDocument.Parse(xml)
List<XElement> xElementList = doc.Element("ServiceUsers").Descendants().ToList();
foreach (XElement element in xElementList)
{
string TEST= element.Element("Name").Value;
comboBoxServiceUser.Items.Add(element.Element("Name").Value);
}

I used the example from XmlSerializer.Deserialize Method as the base for the following snippet that reads the provided xml.
var serializer = new XmlSerializer(typeof(ServiceUsers));
ServiceUsers i;
using (TextReader reader = new StringReader(xml))
{
i = (ServiceUsers)serializer.Deserialize(reader);
}
[XmlRoot(ElementName = "ServiceUsers")]
public class ServiceUsers : List<ServiceUser>
{
}
public class ServiceUser
{
[XmlElement(ElementName = "ID")]
public string Id {get; set;}
}

I think the basis of the problem is your trailing 's' to put it short, You iterate ServiceUser not ServiceUsers
Anyway this runs through fine:
[Fact]
public void CheckIteratorTest()
{
var a = Assembly.GetExecutingAssembly();
string[] resourceNames = a.GetManifestResourceNames();
string nameOf = resourceNames.FirstOrDefault(x => x.Contains("SomeXml"));
Assert.NotNull(nameOf);
using var stream = a.GetManifestResourceStream(nameOf);
Assert.NotNull(stream);
var reader = new StreamReader(stream, Encoding.UTF8);
var serialized = reader.ReadToEnd();
var doc = XDocument.Parse(serialized);
var elemList = doc.Root.Elements("ServiceUser").ToList();
Assert.NotEqual(0, elemList.Count);
foreach(var serviceUser in elemList)
{
System.Diagnostics.Debug.WriteLine($"Name : {serviceUser.Name ?? "n.a."}");
}
}

As being said: XML is case-sensitive. Next issue is .Descendants() returns all the descendant nodes, nested ones, etc, 12 nodes in this case. So NullPointerException will happen even if you fix a "typo".
Here is your fixed code:
XDocument doc = XDocument.Parse(xml);
var xElementList = doc
.Element("ServiceUsers") // picking needed root node from document
.Elements("ServiceUser") // picking exact ServiceUser nodes
.Elements("NAME") // picking actual NAME nodes
.ToList();
foreach (XElement element in xElementList)
{
var TEST = element.Value;
Console.WriteLine(TEST); // do what you were doing instead of console
}

Use doc.Element("ServiceUsers").Elements() to get the<ServiceUser> elements. Then you can loop over the child values of those in a nested loop.
var doc = XDocument.Parse(xml);
foreach (XElement serviceUser in doc.Element("ServiceUsers").Elements()) {
foreach (XElement element in serviceUser.Elements()) {
Console.WriteLine($"{element.Name} = {element.Value}");
}
Console.WriteLine("---");
}
Prints:
ID = 280334
USER_NAME = YVELAMGAMOIYENET12:206322102
UN_ID = 731937
IP = 91.151.136.178
NAME = ?????????????????????: 123456
---
ID = 266070
USER_NAME = ACHIBALANCE:206322102
UN_ID = 731937
IP = 185.139.56.37
NAME = 123456
---
Note: Elements() gets the (immediate) child elements where as Descendants() returns all descendants. Using Elements() gives you a better control and allows you to get the properties grouped by user.
You can also get a specific property like this serviceUser.Element("USER_NAME").Value. Note that the tag names are case sensitive!

how to read XML file and change some value

Xml file :
<configuration>
<work.config>
<variable name="A" value="001" />
<variable name="B" value="002" />
<variable name="C" value="003" />
</work.config>
</configuration>
and next I write some code to read XML
XmlDocument cc = new XmlDocument();
cc.Load("wc.config");
XmlNodeList wc_value = cc.SelectNodes("configuration/work.config[#name='A']");
foreach (XmlNode wc_text in wc_value)
{
String Text2 = wc_text.InnerText;
}
but Text2 is null; why, and how do I have it not null?
And next I want to change name="B" value="999", how do I do that?

Your variable elements dont not have text, that's the reason you are getting null.
Your variable elements have 2 attributes: name and value.
In order to get the value of the attribute:
string txt = wc_text.Attributes["name"].Value
Set value:
wc_text.Attributes["name"].Value = "foo".

Your problem begins in this line.
"configuration/work.config[#name='A']"
work.config attribute doesn't have an attribute called name. Following is what you actually required.
"configuration/work.config/variable[#name='A']"
Similarly, with the path fixed as above, the following line would still return empty string as you are reading the InnerText of the node.
String Text2 = wc_text.InnerText;
What you would need is to read the Value attribute of the node.
String Text2 = wc_text.Attributes["value"].Value;
If your intention is to Read and Update Value Attribute of a particular node, an easier approach would be to use XDocument.
// Assuming there are no duplicate names. You need to change accordingly the Queries if there are duplicates
public void UpdateKey(XDocument document,string key,string value)
{
var node = document.Descendants("variable").First(x=>(string)x.Attribute("name")==key);
node.Attribute("value").Value = value;
}
public string ReadKey(XDocument document, string key)
{
return document.Descendants("variable").First(x=>(string)x.Attribute("name")==key).Attribute("value").Value;
}
Now, you could use it as
XDocument doc = XDocument.Load(xml);
var ValueOfA = ReadKey(doc,"A");
var oldValueOfB = ReadKey(doc,"B");
UpdateKey(doc,"B","999");
var newValueOfB = ReadKey(doc,"B");

LINQ to XML
void Main()
{
XDocument xmlDoc = XDocument.Load(#"e:\temp\wc.config");
// read attributes
foreach (var leaf in xmlDoc.Descendants("variable"))
{
Console.WriteLine(leaf.Attributes("name").FirstOrDefault().Value);
Console.WriteLine(leaf.Attributes("value").FirstOrDefault().Value);
}
// modify value of the attribute
var attr = xmlDoc.Descendants("variable")
.Where(d => (string)d.Attribute("name").Value == "B");
attr.Attributes("value").FirstOrDefault().Value = "999";
}

You could use LINQ to XML to get or set value of any element or attribute based on condition as below:
include namespace System.Xml.Linq in your using directives to use XDocument
XDocument doc = XDocument.Load("wc.config");
foreach (XElement variableElement in doc.Descendants("variable"))
{
if (variableElement.Attribute("name").Value == "A")
{
variableElement.Attribute("value").Value = "";
}
else if (variableElement.Attribute("name").Value == "B")
{
variableElement.Attribute("value").Value = "999";
}
}

Use XPath language:
var xmlString = #"<configuration>
<work.config>
<variable name='A' value='001' />
<variable name='B' value='002' />
<variable name='C' value='003' />
</work.config>
</configuration>";
var xmlDocument = new XmlDocument();
xmlDocument.LoadXml(xmlString);
var variables = xmlDocument.SelectSingleNode("//variable");

Try below code
XmlDocument doc = new XmlDocument();
doc.Load("C:\\config.xml");
XmlNodeList list= doc.SelectNodes("configuration/work.config/variable");
foreach (XmlNode item in list)
{
if (item.Attributes["name"].InnerText == "B")
{
item.Attributes["value"].InnerText = "999";
}
}

XML to List in C#

This is the xml:
<Packages>
<Package>
<Id>1</Id>
<Prerequisites>
<Prerequisite>7</Prerequisite>
<Prerequisite>8</Prerequisite>
</Prerequisites>
</Package>
<Package>
<Id>2</Id>
.....
</Package>
....
</Packages>
And the list:
class lista
{
public int id {get; set;}
public List<int> pre{get;set;}
}
How can I add This xml pattern to a list of lista class and this is what i have got so far bot it only put one in the second list.
XDocument xdoc = XDocument.Load("Employee.xml");
var ListPckage =
(from item in xdoc.Descendants("Package")
orderby item.Element("Id").Value
select new
{
Id = item.Element("Id").Value,
Prerequisite = item.Element("Prerequisites").Element("Prerequisite").Value,
}).ToList();
foreach works for shoing them
foreach (var item in ListPckage)
{
Console.WriteLine(item.Id);
foreach (var item1 in ListPckage)
{
Console.WriteLine(item1.Prerequisites);
}
}

As John Sket mentioned in the comment to the question, one way to achieve that is to use Linq To Xml.
//string xcontent = #"xml content here";
//XDocument xdoc = XDocument.Parse(xcontent);
XDocument xdoc = XDocument.Load("FullPathToXml");
List<lista> resultlist = xdoc.Descendants("Package")
.Select(x=> new lista
{
id = Convert.ToInt32(x.Element("Id").Value),
pre = x.Descendants("Prerequisite").Select(y=>Convert.ToInt32(y.Value)).ToList()
})
.ToList();
But, i'd suggest to use XmlSerialization/XmlDeserialization.

First parse the XML to XDocument using XDocument.Parse to get XML in XDocument variable i.e.
var requiredXml = XDocument.Parse("Xml String here")
Then you can use LINQ to Xml (something like) as below:
//may be syntactic error but you can get an idea
var requiredList =
from element in requiredXml.Descandants("Package")
Select new lista { id = element.Element("ID").Value,
pre = element.Elements("Prerequisite").Select(x=> Convert.ToInt32(x.Value)).ToList() }

Save the same element from XML file as an array C#

it could be a silly question, but i want ta ask, how can I save the same element from an .XML file with different content as an array.
Example XML:
<ithem>
<description>description1</description>
<description>description2</description>
<description>description3</description>
</ithem>
then string [] descriptions will be
descriptions[0] = "description1";
descriptions[1] = "description2";
descriptions[2] = "description3";
Please help!

Using LINQ to XML it would be:
XElement root = XElement.Load(xmlFile);
string[] descriptions = root.Descendants("description").Select(e => e.Value).ToArray();
or
string[] descriptions = root.Element("ithem").Elements("description").Select(e => e.Value).ToArray();

Use XmlDocument to parse the XML :
var map = new XmlDocument();
map.Load("path_to_xml_file"); // you can also load it directly from a string
var descriptions = new List<string>();
var nodes = map.DocumentElement.SelectNodes("ithem/description");
foreach (XmlNode node in nodes)
{
var description = Convert.ToString(node.Value);
descriptions.Add(description);
}
And you get it as an array from:
descriptions.ToArray();

Adding info to a xml file

I have a XML file which contains about 850 XML nodes. Like this:
<NameValueItem>
<Text>Test</Text>
<Code>Test</Code>
</NameValueItem>
........ 849 more
And I want to add a new Childnode inside each and every Node. So I end up like this:
<NameValueItem>
<Text>Test</Text>
<Code>Test</Code>
<Description>TestDescription</Description>
</NameValueItem>
........ 849 more
I've tried the following:
XmlDocument doc = new XmlDocument();
doc.Load(xmlPath);
XmlNodeList nodes = doc.GetElementsByTagName("NameValueItem");
Which gives me all of the nodes, but from here am stuck(guess I need to iterate over all of the nodes and append to each and every) Any examples?

You need something along the lines of this example below. On each of your nodes, you need to create a new element to add to it. I assume you will be getting different values for the InnerText property, but I just used your example.
foreach (var rootNode in nodes)
{
XmlElement element = doc.CreateElement("Description");
element.InnerText = "TestDescription";
root.AppendChild(element);
}

You should just be able to use a foreach loop over your XmlNodeList and insert the node into each XmlNode:
foreach(XmlNode node in nodes)
{
node.AppendChild(new XmlNode()
{
Name = "Description",
Value = [value to insert]
});
}
This can also be done with XDocument using LINQ to XML as such:
XDocument doc = XDocument.Load(xmlDoc);
var updated = doc.Elements("NameValueItem").Select(n => n.Add(new XElement() { Name = "Description", Value = [newvalue]}));
doc.ReplaceWith(updated);

If you don't want to parse XML using proper classes (i.e. XDocument), you can use Regex to find a place to insert your tag and insert it:
string s = #"<NameValueItem>
<Text>Test</Text>
<Code>Test</Code>
</NameValueItem>";
string newTag = "<Description>TestDescription</Description>";
string result = Regex.Replace(s, #"(?<=</Code>)", Environment.NewLine + newTag);
but the best solution is Linq2XML (it's much better, than simple XmlDocument, that is deprecated at now).
string s = #"<root>
<NameValueItem>
<Text>Test</Text>
<Code>Test</Code>
</NameValueItem>
<NameValueItem>
<Text>Test2</Text>
<Code>Test2</Code>
</NameValueItem>
</root>";
var doc = XDocument.Load(new StringReader(s));
var elms = doc.Descendants("NameValueItem");
foreach (var element in elms)
{
element.Add(new XElement("Description", "TestDescription"));
}
var text = new StringWriter();
doc.Save(text);
Console.WriteLine(text);