Please, do note, this solution isn't for everyone. There might be a special case when you'd want that empty dialog. I don't know when or why, but it might happen. Also, you might ask why I keep putting code samples in images. It's because I want you to actually read what you are putting into your own source, and not just copy and paste. Copy and paste isn't a very good practice you know.

Note: I'm using domain prefixes, and if you don't you might have to alter the syntax in some small way to get it working flawlessly for you.

1. Add an entry to the /config/UrlRewriting.config

2. Modify the XSLT so that it outputs a page reference, instead of a querystring.
Was:
Change into:

Note: If you're using directory URLs, you can skip the ".aspx" ending of the link, and just add a slash.

Attempt 1: Adding Add and Insert methods to the Element

public abstract class Element {
public Element() {
this.Children = new List<Element>();
}
public int ID { get; protected set; }
public string Name { get; protected set; }
public virtual Element Parent { get; internal set; }
public virtual List<Element> Children { get; private set; }
public string Instructions { get; set; }

public void Add(Element item){
item.Parent = this;
this.Children.Add(item);
}
...
}

This solution works all-right for many cases, however, it doesn't solve the issue when the Add method is used on the List<Element> directly. We'll want this.

Attempt 2: Changing the List type

public abstract class Element {
public Element() {
this.Children = new ElementList();
}
public int ID { get; protected set; }
public string Name { get; protected set; }
public virtual Element Parent { get; internal set; }
public virtual ElementList Children { get; private set; }
public string Instructions { get; set; }
}

public class ElementList : List<Element> {
public Element Element { get; internal set; }
public ElementList(Element element) {
if (element != null){ this.Element = element; }
else { throw new ArgumentNullException("element"); }
}
new public void Add(Element item) {
if ( item.Parent == null) { item.Parent = Element; }
base.Add(item);
}
new public void Insert(int index, Element item) {
if (item.Parent == null) { item.Parent = Element; }
base.Insert(index, item);
}
new public void InsertRange(int index, IEnumerable<Element> collection){
foreach (Element e in collection){
if (e.Parent == null) { e.Parent = Element; }
}
base.InsertRange(index, collection);
}
new public void AddRange(IEnumerable<Element> collection) {
foreach (Element e in collection) {
if (e.Parent == null) { e.Parent = Element; }
}
base.AddRange(collection);
}
}

This solution ensures that all Elements added to an ElementList, gets their Parent property re-set to reference the ElementLists Element property. This way, one can always assume that an Element's Children, always have their Parent references set.

Next up: Serialization.

public abstract class Element {
public Element() {
this.Children = new List<Element>();
}
public int ID { get; protected set; }
public string Name { get; protected set; }
public virtual Element Parent { get; internal set; }
public virtual List<Element> Children { get; private set; }
public string Instructions { get; set; }
}

The problems:

How to make sure that any objects added to the Children property, gets a correct reference to the parent object (this)?

How to make sure that my object can be serialized in an orderly fashion?

How to enforce that initialization is done properly once the object has been de-serialized?