Parsing XML data in C# and show into ListBox

Question

I am trying to parse a XML file in C# using Visual Studio and show the data in a ListBox, but I don't know how to parse it when I'm dealing with a nested XML file.

This is the code from the XML file:

<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE root [
  <!ELEMENT root (Persons*)>
  <!ELEMENT Persons (name)>
  <!ELEMENT IsMale (#PCDATA)>
  <!ELEMENT Age (#PCDATA)>
  <!ELEMENT Name (#PCDATA)>
  <!ELEMENT LikedPerson (name)>
 ]>
<root>
  <Persons name ="Bob">
    <IsMale>true</IsMale>
    <Age>30</Age>
    <LikedPerson name ="Iulia">
      <IsMale>false</IsMale>
      <Age>32</Age>
    </LikedPerson>
  </Persons>
</root>

The code I've written in C# successfully return me only the name, gender and age for every person, but I don't know how to write to show me also the person_liked:

private void LoadPersons()
    {
        XmlDocument doc = new XmlDocument();
        doc.Load("Baza_de_cunostinte.xml");

        foreach (XmlNode node in doc.DocumentElement) 
        {
            string name = node.Attributes[0].Value;
            int age = int.Parse(node["Age"].InnerText);
            bool isMale = bool.Parse(node["IsMale"].InnerText);

//          Persons likedPerson.name = Persons.node.Attributes[0].Value ?  
//          .....

            listBox.Items.Add(new Persons(name, age, isMale, likedPerson));
        }
    }

    private void listBox_SelectedIndexChanged(object sender, EventArgs e)
    {
        if (listBox.SelectedIndex != -1)
        {
            propertyGrid1.SelectedObject = listBox.SelectedItem;
        }
    }

This is the definition of the Persons.cs :

class Persons
{
    public string Name { get; private set; }
    public int Age { get; private set; }
    public bool IsMale { get; private set; }
    public Persons LikedPerson { get; private set; }

    public Persons(string name, int age, bool isMale, Persons likedPerson)
    {
        Name = name;
        Age = age;
        IsMale = isMale;
        LikedPerson = likedPerson;
    }
}

You'll need to update your class for that as well then, as it stands now it could only occur once in the CLR object. — Dan Field
– Dan Field, Commented Jan 15, 2016 at 15:27

Radin Gospodinov · Accepted Answer · 2016-01-15 12:14:25Z

2

XmlSerializer mySerializer = new XmlSerializer(typeof(Persons));
// Create a FileStream or textreader to read the xml data.
FileStream myFileStream = new FileStream("xmldatafile.xml", FileMode.Open);

var person = (Persons)  mySerializer.Deserialize(myFileStream);

You also need to add constructor without parameter for Persons class.

answered Jan 15, 2016 at 12:14

Radin Gospodinov

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4 Comments

user3063909 Over a year ago

It gives me the following error on the XmlSerializer... line : Proiect_SBC.Persons is inaccessible due to its protection level. Only public types can be processed.

Radin Gospodinov Over a year ago

Make the class definition public: public class Persons{...}

user3063909 Over a year ago

Now I have an error on var person = (Persons) mySerializer.Deserialize(myFileStream); ->> {"There is an error in XML document (10, 2)."}

Dan Field Over a year ago

This is a decent suggestion @RadinGospodinov, but won't work without significant reworking of the class (or the XML)...

Dan Field · Accepted Answer · 2016-01-15 14:24:48Z

The most natural way to do this is to use the XmlSerializer, as suggested, but to do so you'll have to refactor your classes a bit:

[XmlType(Namespace="", TypeName="root")]
public class PersonCollection
{
    [XmlElement(Namespace="", ElementName="Persons")]
    public List<Persons> People { get; set; }
}

public class Persons
{
    [XmlAttribute(AttributeName="name")]
    public string Name { get; set; }
    public int Age { get; set; }
    public bool IsMale { get; set; }

    public Persons LikedPerson { get; set; }

    public Persons() { }

    public Persons(string name, int age, bool isMale, Persons likedPerson)
    {
        Name = name;
        Age = age;
        IsMale = isMale;
        LikedPerson = likedPerson;
    }
}

Then you can do something like this:

XmlSerializer ser = new XmlSerializer(typeof(PersonCollection));

PersonCollection pc = (PersonCollection)ser.Deserialize(File.OpenRead("Baza_de_cunostinte.xml"));
foreach (Persons p in pc.People)
{
   // you now have a fully populated object
}

and the pc.People list will contain your Persons objects.

Eulogy · Accepted Answer · 2016-01-15 16:10:20Z

@user3063909,

1- Use a XSD for the XML definition. Ex:

<xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:element name="root">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="Persons" maxOccurs="unbounded" minOccurs="0" type="Persons"/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>
  <xs:complexType name="Persons">
    <xs:sequence>
      <xs:element type="xs:string" name="IsMale"/>
      <xs:element type="xs:int" name="Age"/>
      <xs:element name="LikedPerson" type="Persons"/>
    </xs:sequence>
    <xs:attribute type="xs:string" name="name" />
  </xs:complexType>
</xs:schema>

2- The Persons class should look like this:

namespace StackOverflow
{
    public class Root
    {
        [XmlElement("Persons")]
        public List<Persons> Persons { get; set; }
    }

    public class Persons
    {
        public string IsMale { get; set; }
        public int Age { get; set; }
        public Persons LikedPerson { get; set; }

        [XmlAttribute("Name")]
        public string Name { get; set; }
    }
}

3- The serializer class:

namespace StackOverflow
{
    public class XmlSerializerHelper<T> where T : class 
    {
        private readonly XmlSerializer _serializer;

        public XmlSerializerHelper()
        {
            _serializer = new XmlSerializer(typeof(T));
        }

        public T BytesToObject(byte[] bytes)
        {
            using (var memoryStream = new MemoryStream(bytes))
            {
                using (var reader = new XmlTextReader(memoryStream))
                {
                    return (T)_serializer.Deserialize(reader);
                }
            }
        }
    }
}

4- And finally, call it this way:

var fileBytes = File.ReadAllBytes("C:/xml.xml");
var persons = new XmlSerializerHelper<Root>().BytesToObject(fileBytes);

The result, will be the root class with a list of persons.

Cheers.

denisv · Accepted Answer · 2016-01-15 12:35:40Z

0

You can get LikedPerson node and get it's name/age like you do now. In order to avoid code duplication, you can create a method, which takes XmlNode, parses it recursively and returns a Person. But the better way is to use XmlSerializer

foreach (XmlNode node in doc.DocumentElement) 
{
    string name = node.Attributes[0].Value;
    int age = int.Parse(node["Age"].InnerText);
    bool isMale = bool.Parse(node["IsMale"].InnerText);

    var likedPerson = node.SelectSingleNode("LikedPerson");

    if (likedPerson != null){
        string name = likedPerson.Attributes[0].Value;
        //age, gender, etc.        
    }        
}

answered Jan 15, 2016 at 12:35

denisv

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3 Comments

user3063909 Over a year ago

I've also added "private System.Xml.XmlNode likedPerson;" in Persons.cs, and now it shows me "LikedPerson" in the PropertyGrid, but it doesn't show anything next to it... (like name, age...)

denisv Over a year ago

Can you update your code, please? I'll try to reproduce your problem.

denisv Over a year ago

I can't comment another answer: There is an error in XML document (10, 2). Your root element is not "Persons", that's why you get this error.

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