Hello,

I am creating a node in a XML file as follows:

private XDocument _context;
_context = XDocument.Load(String.Concat(path, "Slides.xml"),
LoadOptions.SetBaseUri);
// ...
XElement _slide = new XElement("Slide",
new XElement("Id", ???),
new XElement("Name", slide.Name),
new XElement("Published", slide.Published.ToString()),
new XElement("Url", slide.Url)
);
_context.Root.Add(_slide);
_context.Save(new Uri(_context.BaseUri).LocalPath);

I would like the Id to be an incremental unique INT (identity) like as
I use it SQL database.

What is the best way to get the id to be used?

shapper wrote:
On Nov 3, 5:55 pm, Peter Duniho <no.peted.s... at (no spam) no.nwlink.spam.com
wrote:

Hard to say.  I'm not convinced performance is an issue.

After all, to add new elements to your XML, you have to rewrite the XML
file.  Surely that's a lot more expensive than enumerating the existing
elements in the file, and in any case as far as I can tell from your
code example you are reading the entire document into memory to start
with anyway (so the most expensive part of enumerating the elements is
already done).

That is an issue I have.
Is there a way to create, delete, update a node without loading the
entire file?

There's always a way.  :)

Loading the entire file isn't to expensive in terms of performance?

How large is the file?  Most XML files are not large enough to cause a
problem, and the faster the disk, the more physical RAM you have, and
especially if you're using 64-bit Windows, you can get very large
amounts of data in memory all at once without significant problems.

In fact, if you're able to do everything in-memory, it can actually be
faster and easier to code.  After all, at _some_ point, to change an XML
file, you have to read all of the existing data and write all of the new
data.  Whether it's all in memory at the same time is the only thing
that's optional.

If you like, you can follow "A.G."'s suggestion and maintain the current
index count in the document.  But personally, it seems to me that it
would make more sense to just build the document you intend to write
out, and then enumerate all your "Slide" elements, setting the "Id"
explicitly based on a newly-initialized counter.

I need to preserve the same ID's as they are related to something else.
That said is there a way to get the highest ID without loading the
file into memory?

Sure.  You can use the XmlReader class to read through the file without
loading the entire thing into memory at once.  It's just the "document
object model" classes like XmlDocument and XDocument where you have the
whole structure in-memory at once.

That said, XML is a recursive (nested) data structure.  So an XML
document that has a lot of depth can still require a lot of memory
during processing.  But most XML documents are much longer than they are
deep and so a linear parsing provided by XmlReader works fine and uses
much less memory than a DOM approach.

But IMHO DOM is a much more convenient way to do it, and so unless you
expect to have to deal with files that are hundreds of megabytes or
larger, I'd say DOM is the way to go.

If it's really important, write it both ways, measure performance, and
figure out which is faster and more appropriate for your needs.

Pete