Question

I am validating some XML against this XSD:

  <xs:element name="Composite">
    <xs:complexType>
      <xs:sequence minOccurs="0" maxOccurs="unbounded">
        <xs:element name="HeldCurrency" type="mstns:HeldCurrencyType"  nillable="true"/>
        <xs:element name="Component" type="mstns:ComponentType" nillable="true" minOccurs="0"/>
      </xs:sequence>
      <xs:attribute  name="Type" type="mstns:compositeType" use="required"/>
    </xs:complexType>x
  </xs:element>

  <xs:complexType name="HeldCurrencyType">
    <xs:attribute  name="CashPerCreationUnit" type="xs:double" />
    <xs:attribute  name="CashCurrency" type="xs:string" />
    <xs:attribute  name="ClosingSpotFx" type="xs:double" />
  </xs:complexType>

  <xs:complexType name="ComponentType">
    <xs:choice>
      <xs:element name="Weight" type="xs:double"/>
      <xs:element name="Units" type="xs:int"/>
    </xs:choice>
    <xs:attribute name="Symbol" type="xs:string" />
  </xs:complexType>

  <xs:simpleType name="compositeType">
    <xs:restriction base="xs:string">
      <xs:enumeration value="Index" />
      <xs:enumeration value="Etf" />
    </xs:restriction>
  </xs:simpleType>

When I run the following XML against it:

<?xml version="1.0"?>
<Composite xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" Type="Etf" xmlns="urn:xxx-au:index-types">
  <HeldCurrency />
  <Component />
</Composite>

I run this in C#/.Net4.0 with the following code:

using (FileStream fileStream = File.OpenRead("./Xml/Components.xsd"))
{
    using (var schemaReader = new XmlTextReader(fileStream))
    {
        settings.Schemas.Add(null, schemaReader);
        settings.ValidationType = ValidationType.Schema;
        settings.ValidationEventHandler += OnValidationEventHandler;

        using (FileStream infile = File.OpenRead(filename))
        {
            using(var xmlReader = XmlReader.Create(infile,settings))
            {
                var serialiser = new XmlSerializer(typeof (Composite));
                _composite = (Composite) serialiser.Deserialize(xmlReader);
            }
        }
    }
}

I get the following error:
The element ‘Component’ in namespace ‘urn:xxx-au:index-types’ has incomplete content. List of possible elements expected: ‘Weight, Units’ in namespace.
However, I have minOccurs=”0″ so why would this be an issue? It is legal for the sequence to contain no ComponentType elements after all, right?

Thanks in advance.

Answer 1

<xs:element name="Component" type="mstns:ComponentType" nillable="true" minOccurs="0"/>

The minOccurs here is for specifically the “Component” element — not its contents. ComponentType has content of xs:choice, which does not have a minOccurs of 0. So you can omit “Component” entirely, but not its contents.