Question

I have an XML document that I am parsing that does not follow any kind of fixed schema. I need to parse out values by doing something like this:

invoiceDetail.PartNO = invoiceLine.Element(ns + "Item").Element(ns + "ItemID").Element(ns + "ID").Value;

In this example, invoiceLine is of XElement type. The issue is that some nodes do not always exist and in those cases I would prefer to return null or empty instead of returning an error. Is there any way to do this currently or should I just make a special function myself that takes a namespace and a list of element names to attempt to parse into?

Answer 1

XLINQ already does this.
.Element() will return null if there is no element with that name.

To avoid repetitive null checks, use .Elements() instead:

invoiceDetail.PartNO = (string)
    invoiceLine.Elements(ns + "Item")
               .Elements(ns + "ItemID")
               .Elements(ns + "ID")
               .SingleOrDefault();

Each Elements() call will return an IEnumerable<XElement>. If there aren’t any matching elements, it will return an empty sequence, and the rest of the code will still work.

.SingleOrDefault() will convert the final sequence to a single element or null.
The (string) cast calls a custom explicit conversion which should return null if the element was null. You can similarly cast directly to basic value types.