Question

I’m working with an xml fragment, and finding that I’m doing the following a lot:

dim x = xe.Element("foo").Element("bar").Element("Hello").Element("World").Value

however I can’t always guarantee that the xml document will contain foo or bar. Is there a nicer way to do this sort of thing without having to null check every query?

i.e.

dim x = ""
if xe.Element("foo").Any() then
    if xe.Element("foo").Element("bar").Any() Then
        if xe.Element("foo").Element("bar").Element("Hello").Any() Then
            x = xe.Element("foo").Element("bar").Element("Hello").Element("World").ValueOrDefault()
        End If
    End If
End If

(ValueOrDefault is an extension method I’ve added)

Answer 1

Essentially, you’re over analysing the problem.

Start with this:

xe.Elements("foo")

this will return a sequence of all <foo> children of xe; this might be an empty sequence, but will never be null.

Now, extend to this:

xe.Elements("foo")
    .Elements("bar")

This uses extension method Elements() (part of the framework) to look for all <bar> children of the <foo> elements you have so far.

Repeat this the whole way down, until you find the element with a value. Then, use a cast to extract the value:

dim x 
    = (string) xe.Elements("foo")
        .Elements("bar")
            .Elements("Hello")
                .Elements("World")
                    .FirstOrDefault()

Again, the cast is provided by the framework.

All of the checking for null is already handled for you by the smart coders who wrote the framework – this is a large part of what makes XDocument and friends so nice to code with.