Clash Royale CLAN TAG#URR8PPP

XML Serialization error - Invalid or missing value of the choice identifier 'ItemsElementName' of type 'ItemsChoiceType'

I am trying to serialize an object to be passed to a web service and getting the error above. I can see when debugging that the value is present in the object itself but it doesn't seem to be picking this up:

string tradeAreas = new string "Area1", "Area2", "Area3", "Area4";
//RetrieveMarketResultsFor
ItemsChoiceType choices = new ItemsChoiceType ItemsChoiceType.area ;
MarketResultIdentifier mri = new MarketResultIdentifier

ItemsElementName = choices,
Items = tradeAreas,
ItemElementName = ItemChoiceType6.applyingDate,
Item = DateTime.Today.AddDays(-1)
;

var ser = new XmlSerializer(typeof(MarketResultIdentifier));
using (var stream = new FileStream("mri.xml", FileMode.Create))
ser.Serialize(stream, mri);


The web service generated code has the following classes used in the above code:

[System.CodeDom.Compiler.GeneratedCodeAttribute("System.Xml", "4.7.3130.0")]
[System.SerializableAttribute()]
[System.Diagnostics.DebuggerStepThroughAttribute()]
[System.ComponentModel.DesignerCategoryAttribute("code")]
[System.Xml.Serialization.XmlTypeAttribute(Namespace="urn:openaccess")]
public partial class MarketResultIdentifier : OpenAccessAbstractObject

private string itemsField;

private ItemsChoiceType itemsElementNameField;

private object itemField;

private ItemChoiceType6 itemElementNameField;

/// <remarks/>
[System.Xml.Serialization.XmlElementAttribute("area", typeof(string))]
[System.Xml.Serialization.XmlElementAttribute("areaNames", typeof(string))]
[System.Xml.Serialization.XmlChoiceIdentifierAttribute("ItemsElementName")]
public string Items
get
return this.itemsField;

set
this.itemsField = value;



/// <remarks/>
[System.Xml.Serialization.XmlElementAttribute("ItemsElementName")]
[System.Xml.Serialization.XmlIgnoreAttribute()]
public ItemsChoiceType ItemsElementName
get
return this.itemsElementNameField;

set
this.itemsElementNameField = value;



/// <remarks/>
[System.Xml.Serialization.XmlElementAttribute("applyingDate", typeof(System.DateTime), DataType="date")]
[System.Xml.Serialization.XmlElementAttribute("auctionIdentification", typeof(AuctionIdentification))]
[System.Xml.Serialization.XmlElementAttribute("deliveryDay", typeof(System.DateTime), DataType="date")]
[System.Xml.Serialization.XmlChoiceIdentifierAttribute("ItemElementName")]
public object Item
get
return this.itemField;

set
this.itemField = value;



/// <remarks/>
[System.Xml.Serialization.XmlIgnoreAttribute()]
public ItemChoiceType6 ItemElementName
get
return this.itemElementNameField;

set
this.itemElementNameField = value;




/// <remarks/>
[System.CodeDom.Compiler.GeneratedCodeAttribute("System.Xml", "4.7.3130.0")]
[System.SerializableAttribute()]
[System.Xml.Serialization.XmlTypeAttribute(Namespace="urn:openaccess", IncludeInSchema=false)]
public enum ItemsChoiceType

/// <remarks/>
area,

/// <remarks/>
areaNames,


[System.CodeDom.Compiler.GeneratedCodeAttribute("System.Xml", "4.7.3130.0")]
[System.SerializableAttribute()]
[System.Xml.Serialization.XmlTypeAttribute(Namespace="urn:openaccess", IncludeInSchema=false)]
public enum ItemChoiceType6

/// <remarks/>
applyingDate,

/// <remarks/>
auctionIdentification,

/// <remarks/>
deliveryDay,



It fails at line when trying ser.serialize....

Any help appreciated :)

Solution
Turns out this was just down to me being stupid! Thanks to @dbc for pointing this out. My tradeAreas array had 4 items in there (i was using the wrong array here) which it should have only had one!

tradeAreas

Items

ItemsElementName

mri

tradeAreas

choices

tradeAreas

2 Answers
2

When you use XmlChoiceIdentifierAttribute to deserialize a sequence of choice elements into some shared data type (here, string), you need to add two arrays to your data model:

XmlChoiceIdentifierAttribute

string

A property returning an array of objects of appropriate type to capture the choice element contents, here the four string values in the tradeAreas array.

tradeAreas

This first array must be marked with [XmlChoiceIdentifier(name)] where name is the name of the second array, as well as [XmlElement(elementName)] attributes for each possible choice element name.

[XmlChoiceIdentifier(name)]

name

[XmlElement(elementName)]

And a property returning an array of enums to capture the choice element names, here <area> for each element.

<area>

This array must be marked with [XmlIgnore].

[XmlIgnore]

And finally, since the second array captures the element names for the element contents in the first array, the arrays must be in 1-1 correspondence. Thus choices must be initialized to the same length as tradeAreas, e.g. as follows:

choices

tradeAreas

var tradeAreas = new string "Area1", "Area2", "Area3", "Area4";
var choices = Enumerable.Repeat(ItemsChoiceType.area, tradeAreas.Length).ToArray();


In your sample code tradeAreas has four entries while choices has but one, leading to the exception you see.

tradeAreas

choices

Working sample .Net fiddle here.

For documentation on binding to XML choice elements using XmlSerializer, see Choice Element Binding Support: Differentiating by Name as well as XmlChoiceIdentifierAttribute Class: Remarks. For a simple manual example, see e.g. this answer to How to Serialize List<T> property in c# without showing its type in XML serialization.

XmlSerializer

You posted code works provided you add following :

string tradeAreas = null;

public class AuctionIdentification


public class OpenAccessAbstractObject




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