扩展System.Xml.Linq.XElement-内部CloneNode

Question

I have class Foo extending System.Xml.Linq.XElement , but when I call

Foo parent = ..; Foo child = ..; parent.Add(child);

added child is not of type Foo , it is of type XElement .

This is because of internal abstract XNode CloneNode() which is called inside Add method.

I can't override this because of internal. What are my options in this case? I wouldn't like to override each function calling CloneNode() .

Answer 1

For now I have one ugly solution, more like temporary hack than solution, not working generally, just to patch current code. I am not sure that there is any nice solution, other than to rewrite code without extending XElement, so I will post this.

CloneNode is called in Add only when parent field is not null, but Parent property has only get, and parent field is internal. So easiest way to fix my problem is to hide XElement Add with this in XElementExtended:

static FieldInfo parentProperty = typeof(XElementExtended).GetField("parent",
            BindingFlags.NonPublic | BindingFlags.Instance);
public void Add(XElementExtended element)
{
    var el = new XElementExtended(element);
    parentProperty.SetValue(el, null);
    base.Add(el);
}

Answer 2

XElement as an entity is part of the XML model itself. You would extend it if you were adding some functionality to XML like a new kind of Node. And even then, the XNode implementation is still correct because it knows absolutely nothing about your new XML. As far as I know XML isn't extensible it self, eg you can't add a new kind of node.

If you're trying to Typify your XML data then the correct approach will be to build your data model separately and implement read/write methods on the root entities.

If you want to tag your elements then you'll have to either build a wrapper around the whole model straight from XDocument or index the information on the side with Dictionary<XElement, something> .