XML Schema Case Insensitive Enumeration of Simple Type String

Question

I am in need of a case insensitive string enumeration type in my XML schema (.xsd) file. I can get case insensitive by doing the following.

<xs:simpleType name="setDigitalPointType">
    <xs:restriction base="xs:string">
        <xs:pattern value="[Oo][Nn]" />
        <xs:pattern value="[Oo][Ff][Ff]" />
    </xs:restriction>
</xs:simpleType>

The only problem is that I get no enumeration values. I will not get the nice intellesense when using Visual Studio to write my XML. The following will give me enumerations but it is case sensitive.

<xs:simpleType name="setDigitalPointType">
    <xs:restriction base="xs:string">
        <xs:enumeration value="on" />
        <xs:enumeration value="off" />
    </xs:restriction>
</xs:simpleType>

This will give me my enumerations but if I ever receive a value of "On", "ON", or "oN" it will fail verification.

I want enumeration of "on", "off" and allow entry of case insensitive versions.

Answer 1

If you want to both keep the case-insensitive validation, while still getting Intellisense in Visual Studio 2010, you can use a union:

<xs:simpleType name="setDigitalPointType">
    <xs:union>
        <xs:simpleType>
            <xs:restriction base="xs:string">
                <xs:enumeration value="on" />
                <xs:enumeration value="off" />
            </xs:restriction>
        </xs:simpleType>
        <xs:simpleType>
            <xs:restriction base="xs:string">
                <xs:pattern value="[Oo][Nn]" />
                <xs:pattern value="[Oo][Ff][Ff]" />
            </xs:restriction>
        </xs:simpleType>
    </xs:union>
</xs:simpleType>

This works because it exploits the fact that Visual Studio 2010 only processes the first simple type in a union when it builds it's Intellisense data. However when it validates a document, it processes both, which means "On" is still determined to be valid even though it isn't in the list of enumeration values.