C＃中的XML元素和属性等效项是什么？

Question

I am trying to define C# objects based on this XML:

<UPDs LUPD="86">
  <UPD ID="106">
    <ER R="CREn">
      <NU UID="1928456" />
      <NU UID="1886294" />
      <M>
        <uN>bob · </uN>
        <mO>fine :D</mO>
      </M>

So far I have:

public class UDPCollection    
{
    List<UDP> UDPs; 

    public UDPCollection()
    {
        UDPs = new List<UDP>();
    }
}

public class UDP
{
    public int Id;
    public List<ER> ERs;
    public UDP(int id, List<ER> ers)
    {
        Id = id;
        ERs = ers;
    }
}

public class ER
{
    public string LanguageR;

    public ER(string languager)
    {
        LanguageR = languager;
    }
}

My questions: What do elements map to in C#? Classes? What do attributes map to? Properties? Am I going about this the correct way?

Answer 1

Use the XmlSerializer class and the XmlRoot , XmlElement and XmlAttribute attributes. For example:

using System.Xml.Serialization;

...

[XmlRoot("UPDs")]
public class UDPCollection
{
    // XmlSerializer cannot serialize List. Changed to array.
    [XmlElement("UPD")]
    public UDP[] UDPs { get; set; }

    [XmlAttribute("LUPD")]
    public int LUPD { get; set; } 

    public UDPCollection()
    {
        // Do nothing
    }
}

[XmlRoot("UPD")]
public class UDP
{
    [XmlAttribute("ID")]
    public int Id { get; set; }

    [XmlElement("ER")]

    public ER[] ERs { get; set; }

    // Need a parameterless or default constructor.
    // for serialization. Other constructors are
    // unaffected.
    public UDP()
    {
    }

    // Rest of class
}

[XmlRoot("ER")]
public class ER
{
    [XmlAttribute("R")]
    public string LanguageR { get; set; }

    // Need a parameterless or default constructor.
    // for serialization. Other constructors are
    // unaffected.
    public ER()
    {
    }

    // Rest of class
}

The code to write out the XML is:

using System.Xml.Serialization;

...

// Output the XML to this stream
Stream stream;

// Create a test object
UDPCollection udpCollection = new UDPCollection();
udpCollection.LUPD = 86;
udpCollection.UDPs = new []
{
    new UDP() { Id= 106, ERs = new [] { new ER() { LanguageR = "CREn" }}}
};

// Serialize the object
XmlSerializer xmlSerializer = new XmlSerializer(typeof(UDPCollection));
xmlSerializer.Serialize(stream, udpCollection);

Not that the XmlSerializer adds additional namepsaces but it can parse XML without them if needed. The output of the above is:

<?xml version="1.0"?>
<UPDs xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
        xmlns:xsd="http://www.w3.org/2001/XMLSchema" LUPD="86">
    <UPD ID="106">
       <ER R="CREn" />
    </UPD>
</UPDs>

Use the Deserialize() method to parse it from XML into an object.

Answer 2

XML elements and attributes don't necessarily map to anything in particular in C#. You can make them map to classes and properties if you want, but it's not required.

That said, if you want to map your existing XML to some sort of C# data structures, the way you're doing it seems reasonable - I'd just recommend replacing your public fields with actual properties, and maybe making the list properties a less specific type - say, IEnumerable, or ICollection, or IList if they really need to be in order.