Q:

XML Serialized from xsd.exe generated code using substitution groups is invalid (invalid xsi:type error)

I've generated some C# classes from some 3GPP XSDs (multiple XSD files/namespaces) and it works great for serialization apart from one problem with concrete instances of an abstract type used in a substitution group.
Firstly, the relevant parts of the schema:
(genericNrm.xsd)
<element name="ManagedElement">
    <complexType>
      <complexContent>
        <extension base="xn:NrmClass">
          <sequence>
            ...
            <choice minOccurs="0" maxOccurs="unbounded">
              <element ref="xn:IRPAgent"/>
              <element ref="xn:ManagedElementOptionallyContainedNrmClass"/>
              <element ref="xn:VsDataContainer"/>
            </choice>
          </sequence>
        </extension>
      </complexContent>
    </complexType>
</element>

<element
    name="ManagedElementOptionallyContainedNrmClass"
    type="xn:NrmClass"
    abstract="true"
/>

(eutran.xsd)
<element name="ENBFunction" substitutionGroup="xn:ManagedElementOptionallyContainedNrmClass">
    <complexType>
      <complexContent>
        <extension base="xn:NrmClass">
          <sequence>
            <element name="attributes" minOccurs="0">
              <complexType>
                <all>
                  <element name="userLabel" type="string" minOccurs="0"/>
... etc

The XML serialised from a simple ManagedElement with contained ENBFunction is:
<ManagedElement xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" id="1234" xmlns="http://www.3gpp.org/ftp/specs/archive/32_series/32.625#genericNrm">
    <ManagedElementOptionallyContainedNrmClass xmlns:q1="http://www.3gpp.org/ftp/specs/archive/32_series/32.765#eutranNrm" xsi:type="q1:ENBFunction" id="1234">
      <q1:attributes>
        <q1:userLabel>label</q1:userLabel>
      </q1:attributes>
    </ManagedElementOptionallyContainedNrmClass>
  </ManagedElement>

The built in visual studio XML validation complains about the  element, stating "This is an invalid xsi:type 'http://www.3gpp.org/ftp/specs/archive/32_series/32.765#eutranNrm:ENBFunction'.
So is the serialized XML wrong or the validation?  Is it something to do with the separate namespaces?
I can deserialize the XML just fine but I need the generated XML to be schema compliant (without changing the schemas).  I found that if I manually change the XML to the following, the error disappears (and I find it easier to read also):
<ManagedElement xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" id="1234" xmlns="http://www.3gpp.org/ftp/specs/archive/32_series/32.625#genericNrm">
    <q1:ENBFunction xmlns:q1="http://www.3gpp.org/ftp/specs/archive/32_series/32.765#eutranNrm" id="1234">
      <q1:attributes>
        <q1:userLabel>label</q1:userLabel>
      </q1:attributes>
    </q1:ENBFunction>
</ManagedElement>

Can I force the serializer to output it this way?
Thanks for looking...

A:

I solved this by manually editing the code generated from the XSD.  An XmlElementAttribute is needed on the ManagedElement classes Items collection to ensure the serialisation works correctly:
[System.CodeDom.Compiler.GeneratedCodeAttribute("xsd", "4.0.30319.1")]
[System.SerializableAttribute()]
[System.Diagnostics.DebuggerStepThroughAttribute()]
[System.ComponentModel.DesignerCategoryAttribute("code")]
[System.Xml.Serialization.XmlTypeAttribute(AnonymousType=true, Namespace="http://www.3gpp.org/ftp/specs/archive/32_series/32.625#genericNrm")]
[System.Xml.Serialization.XmlRootAttribute(Namespace="http://www.3gpp.org/ftp/specs/archive/32_series/32.625#genericNrm", IsNullable=false)]
public partial class ManagedElement : NrmClass {

...

[System.Xml.Serialization.XmlElementAttribute("ENBFunction", typeof(ENBFunction), Namespace = "http://www.3gpp.org/ftp/specs/archive/32_series/32.765#eutranNrm")]
public NrmClass[] Items {
...

This attribute is required for all classes inherited from ManagedElement to ensure the correct one is used at serialization time.

