Expression in XML Literal Processing Instruction?

Question

Why doesn't the <?qbxml...?> line work?  Is there a way to embed an expression in a processing instruction?  If I remove the <?qbxml...?> line, then it produces valid xml. With the line it won't compile.

        Dim qbXmlRq2 As XDocument =
            <?xml version="1.0"?>
            <?qbxml version=<%= QBXMLVer %>?>
            <QBXML>
                <QBXMLMsgsRq onError="stopOnError">
                    <<%= transType & "QueryRq" %> requestID=<%= ReferenceNumber %>>
                        <RefNumber><%= ReferenceNumber %></RefNumber>
                        <IncludeLineItems>1</IncludeLineItems>
                        <OwnerID>0</OwnerID>
                    </>
                </QBXMLMsgsRq>
            </QBXML>

Answer 1

According to http://msdn.microsoft.com/en-us/library/bb385055.aspx you can't use expressions in a VB.NET processing instruction literal.

Processing instructions can take any data, while they are often used to contain pseudo attributes in 'name="value"' syntax that is not the only allowed syntax.

If you want to construct a processing instruction data dynamically then I don't think you can use a literal, you will need to use code as in

        Dim QBXMLVer As String = "test-1.0"
        Dim doc As XDocument =
            <?xml version="1.0"?>
            <Root>
                <Foo>Bar</Foo>
            </Root>

        doc.AddFirst(New XProcessingInstruction("qbxml", String.Format("version=""{0}""", QBXMLVer)))

that creates

<?qbxml version="test-1.0"?>
<Root>
  <Foo>Bar</Foo>
</Root>

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