Access Elements in XSD to C# Class With xs:Choice - class

Question

I have read several dozen articles on the xs:Choice XSD element but cant wrap my head around how we are supposed to use the resulting class. Here is the XSD element and the class conversion from Xsd2Code++:
<xs:element name="VariantRoads">
<xs:complexType>
<xs:choice minOccurs="0" maxOccurs="unbounded">
<xs:element ref="Variant" minOccurs="0"/>
<xs:element ref="DepVariant"/>
<xs:element ref="ArrVariant"/>
</xs:choice>
</xs:complexType>
</xs:element>
[XmlArrayItemAttribute("ArrVariant", typeof(ArrVariantType), IsNullable = false)]
[XmlArrayItemAttribute("DepVariant", typeof(DepVariantType), IsNullable = false)]
[XmlArrayItemAttribute("Variant", typeof(VariantType), IsNullable = false)]
public object[] VariantRoads
{
get
{
return _variantRoads;
}
set
{
_variantRoads = value;
}
}
So that compiles and now I am ready to start populating my main class.
BaseRoadType brd = new BaseRoadType();
brd.VariantRoads = = new object[3]; // not sure how to initialize
brd.VariantRoads[0] = ??? // how do I assign my property
I am just really lost on how I should populate the VariantRoads class and then read it later and determine what choice was made.

Answer 1

The XmlArrayItemAttribute attributes at the top of the public object[] VariantRoads declaration gives you type hints that are acceptable element values of the array.
An xs:choice is meant to model just one of multiple possibilities - but there's also the maxOccurs="unbounded" attribute set on the choice definition, which turns the type declaration to an object array object[].
The choice definition reads in plain English as basically 'zero or many choices of ("ArrVariant", "DepVariant", "Variant") elements'
So this is acceptable:
BaseRoadType brd = new BaseRoadType();
brd.VariantRoads = new object[1] {
new ArrVariant()
};
Andt this is too:
brd.VariantRoads = new object[3] {
new Variant(), new ArrVariant(), new DepVariant(),
};
And also multiple instances of the same type:
brd.VariantRoads = new object[2] {
new ArrVariant(), new ArrVariant(),
};
Because each element in the array represents your 'choice' of the possible 3, the maxOccurs="unbounded" also means you can have more than one choice (hence the array).
To take it further, if the choice definition didn't have the maxOccurs="unbounded", the generated code would probably look like this:
[XmlArrayItemAttribute("ArrVariant", typeof(ArrVariantType), IsNullable = false)]
[XmlArrayItemAttribute("DepVariant", typeof(DepVariantType), IsNullable = false)]
[XmlArrayItemAttribute("Variant", typeof(VariantType), IsNullable = false)]
public object VariantRoad { get; set; }
Meaning you could only have one choice.