Can't deserialize an element if declared as attribute in my class and appears as element

Question

I'm receiving XML files with different layouts:

<?xml version="1.0" encoding="UTF-8"?>
<Response>
    <PInstrument>
        <Type>myType</Type>
        <Data>
            <PB>blabla</PB>
            <MP>blabla</MP>
            <Mode>blabla</Mode>
        </Data>
    </PInstrument>
</Response>

or

<?xml version="1.0" encoding="UTF-8"?>
<Response>
    <PInstrument>
        <Type>myType</Type>
        <Data PB="blabla" MP="blabla" Mode="blabla" />
    </PInstrument>
</Response>

In XML both are perfectly correct, but here data contains either attributes or elements.

In .NET, to retrieve the XML inside an object, I must declare it but must specify whether this is an element or an attribute. As a matter of fact the XSD defines what's inside data as attributes so XSD created them as attributes.

But when I read the XML where they are elements, they simply don't populate as if the XmlDeserialize made a difference, though there's not in the standard as indicated in the W3C specs.

Why is .NET forcing elements to be elements and attributes to be attributes?

Is there a way to deserialize the file no matter the representation (attribute or element)?

Xml Serialization is not meant for random XML file. The xml file for serialization to work must always be well structured. — jdweng, Aug 31 '23 at 20:02

score 1 · Answer 1 · answered Aug 31 '23 at 20:40

I would use json for example

    using Newtonsoft.Json;

    var x = XElement.Parse(xml);

    var response =JObject.Parse(JsonConvert.SerializeXNode(x)
                .Replace("\"@", "\""))
                .ToObject<Root>();

c# classes

public class Root
{
    public Response Response { get; set; }
}

public class Data
{
    public string PB { get; set; }
    public string MP { get; set; }
    public string Mode { get; set; }
}

public class PInstrument
{
    public string Type { get; set; }
    public Data Data { get; set; }
}

public class Response
{
    public PInstrument PInstrument { get; set; }
}

That's interesting to consider using JSON to work with XML but there's a point here indeed. I'm going to investigate that — philippe, Aug 31 '23 at 21:34

score 1 · Answer 2 · answered Sep 02 '23 at 05:54

An attribute and child element of an XML element can have the same name, which may be one reason why .NET forces elements to be elements and attributes to be attributes.^[1] I.e. the following is perfectly well-formed XML

<Data PB="foo">
  <PB>bar</PB>
</Data>

XmlSerializer allows you to bind to both the PB attribute and child element to distinct .NET properties.

In fact, this provides a workaround for your problem: you could create surrogate properties for each attribute that redirect the value of each to the property binding to the corresponding element, like so:

[XmlRoot("Data")]
public class Data
{
    [XmlElement("PB")] public string PB { get; set; }
    [XmlElement("MP")] public string MP { get; set; }
    [XmlElement("Mode")] public string Mode { get; set; }

    [XmlAttribute("PB")] public string PBAttribute { get => PB; set => PB = value; }
    [XmlAttribute("MP")] public string MPAttribute { get => MP; set => MP = value; }
    [XmlAttribute("Mode")] public string ModeAttribute { get => Mode; set => Mode = value; }

    // Prevent the elements from being re-serialized.
    public bool ShouldSerializePB() => false;
    public bool ShouldSerializeMP() => false;
    public bool ShouldSerializeMode() => false;
}

[XmlRoot("PInstrument")]
public class PInstrument 
{
    public string Type { get; set; }
    public Data Data { get; set; }
}

[XmlRoot("Response")]
public class Response 
{
    public PInstrument PInstrument { get; set; }
}

Demo fiddle here.,

This version of <Data> always re-serializes the values as attributes. If you need to track whether the values were deserialized as attributes or elements and re-serialize accordingly, you could use the {PropertyName}Specified pattern:

[XmlRoot("Data")]
public class Data
{
    [XmlElement("PB")] public string PB { get; set; }
    [XmlElement("MP")] public string MP { get; set; }
    [XmlElement("Mode")] public string Mode { get; set; }

    [XmlAttribute("PB")] public string PBAttribute { get => PB; set => PB = value; }
    [XmlAttribute("MP")] public string MPAttribute { get => MP; set => MP = value; }
    [XmlAttribute("Mode")] public string ModeAttribute { get => Mode; set => Mode = value; }

    [XmlIgnore] public bool PBSpecified { get; set; } = false; // Serialize as attributes unless specified.
    [XmlIgnore] public bool MPSpecified { get; set; } = false;
    [XmlIgnore] public bool ModeSpecified { get; set; } = false;

    [XmlIgnore] public bool PBAttributeSpecified { get => !PBSpecified; set => PBSpecified = !value; }
    [XmlIgnore] public bool MPAttributeSpecified { get => !MPSpecified; set => MPSpecified = !value; }
    [XmlIgnore] public bool ModeAttributeSpecified { get => !ModeSpecified; set => ModeSpecified = !value; }
}

Demo fiddle #2 here.

^[1] Elements and attributes also appear differently in XSD schemas and have different restrictions on the types of values they can contain.

Can't deserialize an element if declared as attribute in my class and appears as element

2 Answers2