Order of elements in choice

[Dobrygnom]

Hi, I have a problem similar to #285 and looking for solution/workaround.

I have an xml which contains sequence of Plus/Minus elements (simplified here) and their order matters to the backend.

<Operation>
    <Plus></Plus>
    <Plus></Plus>
    <Minus></Minus>
    <Plus></Plus>
</Operation> 

And following xsd which utilizes choice.

<?xml version="1.0" encoding="utf-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:generic="file://generic.xsd" elementFormDefault="qualified" attributeFormDefault="unqualified">
    <xs:complexType name="Operation">
        <xs:choice maxOccurs="unbounded">
                <xs:element name="Plus"   type="PlusType"/>
                <xs:element name="Minus"  type="MinusType"/>
        </xs:choice>
    </xs:complexType>
    <xs:complexType name="PlusType"/>
    <xs:complexType name="MinusType"/>

</xs:schema>

With code generated by XmlSchemaClassGenerator I can't figure out how to preserve order of Plus/Minus operations, because it always dumps all the Plus elements first and Minus after.
It worked fine with xsd.exe generated code, but with XmlSchemaClassGenerator handling choice differently - I can't figure out how to work around the problem without changing xsd to use xs:any which is much worse than what xsd.exe generates.

[mganss]

Use substitution groups:

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" 
    elementFormDefault="qualified"
    attributeFormDefault="unqualified">
    <xs:element name="Operation">
        <xs:complexType>
            <xs:sequence>                
                <xs:element 
                    ref="OperationElement" 
                    minOccurs="0" 
                    maxOccurs="unbounded"/>
            </xs:sequence>
        </xs:complexType>
    </xs:element>
    <xs:element name="OperationElement" type="OperationType"  abstract="true"/>
    <xs:element name="Plus" type="PlusType"  substitutionGroup="OperationElement"/>
    <xs:element name="Minus" type="MinusType" substitutionGroup="OperationElement"/>
    <xs:complexType name="OperationType" />
    <xs:complexType name="PlusType">
        <xs:complexContent>
            <xs:extension base="OperationType" />
        </xs:complexContent>
    </xs:complexType>
    <xs:complexType name="MinusType">
        <xs:complexContent>
            <xs:extension base="OperationType" />
        </xs:complexContent>
    </xs:complexType>
</xs:schema>