"Oliver Sturm" <ol****@sturmnet.org> wrote in message news:ey****************@tk2msftngp13.phx.gbl...
When I serialize a Data instance, said SubData instance is written to the XML file twice. After deserialization I have two
different objects instead of one that's in both lists.
How can I change this?
What it sounds like you're looking for are "multi-reference accessors" (MRAs)
which is how SOAP rpc/encoded messages preserve the notion of an object's
identity.
The way MRAs work, and what gives them the ability to distinguish whether
a pair of objects have the same value or actually refer to the same instance,
is because the objects' values are each given a unique 'id' attribute and get
serialized outside of the list itself while the list contains references having an
'href' attribute into the set of serialized objects.
As an example, if I had a four-Person object array,
<SOAP-ENC:Array SOAP-ENC:arrayType="a1:Person[4]" xmlns:a1="http://www.example.com/">
<item href="#ref-1"/> <!-- Derek -->
<item href="#ref-2"/> <!-- Amy -->
<item href="#ref-3"/> <!-- Bob -->
<item href="#ref-2"/> <!-- Amy -->
</SOAP-ENC:Array>
<a1:Person id="ref-1" xmlns:a1="http://www.example.com/">
<Name id="ref-4">Derek</Name>
</a1:Person>
<a1:Person id="ref-2" xmlns:a1="http://www.example.com/">
<Name id="ref-5">Amy</Name>
</a1:Person>
<a1:Person id="ref-3" xmlns:a1="http://www.example.com/">
<Name id="ref-6">Bob</Name>
</a1:Person>
This would de-serialize into an array of four Person elements, but the 2nd and 4th
entries in that Person[] would both be 'Amy.' Not just a Person object with the
Name of 'Amy,' but the exact same object reference.
How do you get this in .NET?
Use the SoapFormatter, from the System.Runtime.Serialization.Formatters.Soap
namespace (add a reference to the .dll of the same name.) The above XML was
serialized with the following simple piece of code,
// Ensure your Person class is marked [Serializable] and has a default ctor.
Person p1 = new Person( "Derek");
Person p2 = new Person( "Amy");
Person p3 = new Person( "Bob");
Person[] people = new Person[] { p1, p2, p3, p2 };
// . . .
SoapFormatter formatter = new SoapFormatter( );
formatter.Serialize( fstream, people);
SoapFormatter is going to put all of this into a SOAP envelope, so if you don't
want that in your serialization then you can subclass a Stream class to intercept
and filter out any text written to it where the line of text starts with "<SOAP-ENV"
or "</SOAP-ENV".
Derek Harmon
