Question

I have a situation where I have an xml file that I don’t want to modify. The AddAnnotation function in XElement class provides an option to add memory-only data which is not serialized and not part of the XML.

I want to be able to save these annotations (for example: to another xml file) and then to deserialize both the xml and the annotations in order to get the same object I had.

I don’t want to change the original xml and that’s the reason that I use annotations.

To summarize, I want to be able to add custom data to an xml file. This data won’t be a part of the xml when I serialize it or it will be a part of the xml but I would be able to retrieve the original xml easily.

Do you have any recommendation how I can do such a thing?

Edit: Should I use xml processing instructions? Are processing instructions intended for this kind of usage?

Answer 1

It sounds to me like the simplest approach would be to use regular nodes, but in a different xml namespace – i.e.

<foo standardAttrubute='abc' myData:customAttribute='def'>     <standardElement>ghi</standardElement >     <myData:customElement>jkl</myData:customElement> </foo> 

(where myData is an xmlns alias for the namespace-uri)

In many cases, readers are only checking for data in their namespace (or the default/blank namespace) – values in custom namespaces are generally skipped.

To get pack the original xml, one simple approach would be to run it through an xslt that only respects the default/original namespace.

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XNamespace myData = XNamespace.Get('http://mycustomdata/'); XElement el = new XElement('foo',     new XAttribute(XNamespace.Xmlns + 'myData', myData.NamespaceName),     new XAttribute('standardAttribute', 'abc'),     new XAttribute(myData + 'customAttribute', 'def'),     new XElement('standardElement', 'ghi'),     new XElement(myData + 'customAttribute', 'jkl')); string s = el.ToString(); 

To remove such data from an XElement, perhaps:

    static void Strip(XElement el, XNamespace ns) {         List<XElement> remove = new List<XElement>();         foreach (XElement child in el.Elements()) {             if (child.Name.Namespace == ns) {                 remove.Add(child);             } else {                 Strip(child, ns);             }         }         remove.ForEach(child => child.Remove());          foreach (XAttribute child in             (from a in el.Attributes()              where a.Name.Namespace == ns              select a).ToList()) {             child.Remove();         }     }