Insering a node via an expression

[Jan Limpens]

Hello,

I am creating a simple CRUD application which uses xml files as data
storage. I extended Textbox with a XPath expression and a XmlDocument
property, this way I can easily read and update existing nodes' content.
I was very happy with the solution until the first time I needed to
insert a hierarchy of nodes. Imagine the following situation:

<Entry>
<Version xml:lang="en">
<Text>foo</Text>
</Version>
<Version xml:lang="de">
<Text>fu</Text>
</Version>
</Entry>

I select "<Entry/Version[lang('fr')]/Text" and receive null. There is no
such node, so I wanted it to be created - but how???
Of course I could hard code every conceivable situation in c#, but ... I
don't have to go into this. Something like this must have a somehow
expression triggered mechanism that does the dirty work. I would not
even know which syntax to use.

I could chop my expression into pieces and iterate it backwards until I
find a valid node - in this case <Entry>, then I would have to create
the counterpart of "Version[lang('fr')]" - which is <Version
xml:lang="fr">, but I needed to implement all XPath & DOM functions, to
be able to guess that.

Schema could help me. If my XmlDocument had a schema it would be somehow
possible to construct a prototype xml fragment that I could insert in
the right spot, but this in interaction with XPath goes way beyond my
programming skills.

Inventing a XPath inspired insert syntax like
XmlNode myNode =
XmlInserter.InsertNode("/Entry/Version@xml:lang='de'@something='xx'/Title");
myNode.InnerText = "bar";
does not seem a good idea to me. That's something consortiums do...

I cannot imagine that this problem is so uncommon, that there are no
proven solutions for it. I am just being blind and/or unimaginative, I
guess. As I am pretty lost, I'd be extremely happy for any hint into the
right direction!

Jan

[John Saunders]

"Jan Limpens" <1s*****@lastname.comwrote in message
news:O0**************@TK2MSFTNGP05.phx.gbl...

I cannot imagine that this problem is so uncommon, that there are no
proven solutions for it. I am just being blind and/or unimaginative, I
guess. As I am pretty lost, I'd be extremely happy for any hint into the
right direction!

Jan, you're not the only person who has wanted a way to create an XML
document, or pieces of one, from a schema. Unfortunately, there was no
solution for the others, either.

This may, in part, be due to the fact that your problem statement
presupposes the solution to the problem. To restate:

1) Given a text box combined with an XPath expression and an XmlDocument,
and
2) Given that the XPath expression, when applied to the XmlDocument,
provides the content of the text box, then

How do you use the changed content of the text box to create the node or
nodes implied by the XPath expression?

The above requires the solution to your larger problem (creating nodes if
they didn't exist) to be in terms of your smaller problem (displaying the
nodes if they exist). It's possible that you need to solve the larger
problem first, after which the smaller problem will solve itself.
Another suggestion I would make would be that you should separate data and
presentation. Tying a presentation element to data storage is a bad
architecture. Among other problems that come to mind, how would you handle
a combo box or even radio buttons? This simple concept of an XPath
expression doesn't adequately cover even the most basic user interface
elements, once you get past text boxes.

Even with text boxes, your paradigm doesn't seem to cover validation.

I think you should probably broaden your problem definition, after which
you'll realize that this is not a problem that can be solved by one person.

I would wish to draw your attention, and that of anyone else with a similar
problem, to a commercial solution to this general problem of producing a
CRUD user interface based on XML Schema: Microsoft Office InfoPath
(http://msdn.microsoft.com/office/program/infopath/). Even if you strip off
all the fancy "Office" features, you'll find that the work involved in
creating a general solution to this XML Schema UI problem is substantial.

John