Reading multiple XML attributes

Question

I'm trying to get information from XML library (file below) using C# in Visual Studio.

<buttons>
<measurement>
    <scan id="0" time="20 53 06">
        <q address="40" state="0"/>
        <q address="41" state="0"/>
        <q address="42" state="1"/>
        <q address="43" state="0"/>
        <q address="44" state="1"/>
        <q address="45" state="1"/>
        <q address="46" state="1"/>
        <q address="47" state="1"/>
    </scan>
</measurement>
<measurement>
    <scan id="1" time="20 53 07">
        <q address="40" state="0"/>
        <q address="41" state="0"/>
        <q address="42" state="0"/>
        <q address="43" state="0"/>
        <q address="44" state="1"/>
        <q address="45" state="0"/>
        <q address="46" state="0"/>
        <q address="47" state="0"/>
    </scan>
</measurement>
<measurement>
    <scan id="2" time="20 53 08">
        <q address="40" state="0"/>
        <q address="41" state="1"/>
        <q address="42" state="0"/>
        <q address="43" state="1"/>
        <q address="44" state="1"/>
        <q address="45" state="0"/>
        <q address="46" state="0"/>
        <q address="47" state="1"/>
    </scan>
</measurement>
<measurement>
    <scan id="3" time="20 53 09">
        <q address="40" state="1"/>
        <q address="41" state="0"/>
        <q address="42" state="0"/>
        <q address="43" state="1"/>
        <q address="44" state="1"/>
        <q address="45" state="0"/>
        <q address="46" state="1"/>
        <q address="47" state="0"/>
    </scan>
</measurement>
<measurement>
    <scan id="4" time="20 53 10">
        <q address="40" state="0"/>
        <q address="41" state="0"/>
        <q address="42" state="1"/>
        <q address="43" state="1"/>
        <q address="44" state="1"/>
        <q address="45" state="1"/>
        <q address="46" state="0"/>
        <q address="47" state="0"/>
    </scan>
</measurement>
<measurement>
    <scan id="5" time="20 53 11">
        <q address="40" state="1"/>
        <q address="41" state="1"/>
        <q address="42" state="1"/>
        <q address="43" state="0"/>
        <q address="44" state="0"/>
        <q address="45" state="0"/>
        <q address="46" state="1"/>
        <q address="47" state="0"/>
    </scan>
</measurement>
<measurement>
    <scan id="6" time="20 53 12">
        <q address="40" state="0"/>
        <q address="41" state="1"/>
        <q address="42" state="1"/>
        <q address="43" state="0"/>
        <q address="44" state="0"/>
        <q address="45" state="1"/>
        <q address="46" state="1"/>
        <q address="47" state="1"/>
    </scan>
</measurement>
<measurement>
    <scan id="7" time="20 53 13">
        <q address="40" state="1"/>
        <q address="41" state="1"/>
        <q address="42" state="1"/>
        <q address="43" state="1"/>
        <q address="44" state="1"/>
        <q address="45" state="0"/>
        <q address="46" state="1"/>
        <q address="47" state="1"/>
    </scan>
</measurement>

it is my first attempt to do and read xml files.

Hre is what i want to do:
I want to inpud ID and program schould return all q states in array.

Here is what I tried:

using System.Xml;
XmlDocument xmlDoc = new XmlDocument();
xmlDoc.Load("Path to my xml");
XmlNodeList titleNodes = xmlDoc.SelectNodes("//buttons/measurment/scan/q");
foreach(XmlNode titleNode in titleNodes)
    Console.WriteLine(titleNode.Attribute["address"]);
Console.ReadKey();

I know that this code will only display some q atributes in console. I never went furder because it is not working (nothing appears in console window) . And i dont know why. I just don understand this XmlRead, XmlDeocument. I was learnig form here: Tutorial . I was folowing every stem and examlpes. Only XmlRead giave something to me. Bu it reads just everything, not specific regions.

Can you show me some examples or solutions?

Answer 1

Consider using XDocument , which allows you to use LINQ, making your xml life easier:

string myId = "2";

var doc = XDocument.Parse(xmlString); //or XDocument.Load(filePath)

//find the correct 'scan' node based on your id
var scan = doc.Descendants("scan")
              .FirstOrDefault(s => s.Attribute("id").Value == myId);

//grab all q's and get their 'state' for that 'scan' node
var states = scan?.Descendants("q")
                  .Select(q => q.Attribute("state").Value);

foreach (var state in states)
{
    Console.WriteLine(state);
}

Answer 2

Assuming the xml is well formed and the root node is corectly closed, you have a typo in the string measurement and this is correctly selecting all the q tags

XmlNodeList titleNodes = xmlDoc.SelectNodes("//buttons/measurement/scan/q");

If you want only the ones under one id

XmlNodeList titleNodes = xmlDoc.SelectNodes("//buttons/measurement/scan[@id=2]/q") ;

If there is no such id, you'll get an empty collection but not an exception error: so that case is managed.

Finally, don't forget the Value field

Console.WriteLine(titleNode.Attributes["address"].Value);

Answer 3

XmlNodeList titleNodes = xmlDoc.SelectNodes("//measurement/scan/q");

然后，您将获得64件物品。