Elegant way to deal with null references in chained XElement axis methods

Question

Given something like this:

var results = theElement.Element("Blah").Element("Whatever").Elements("Something");

Is there an elegant way to deal with a null Blah or Whatever element so results is just null or empty in these cases?

I know I can split up the query and manually do these checks but was wondering if there was something more succinct.

Answer 1

You can add some extension methods to do this for you. For the Element method you would return null or the element itself. For the Elements method you would return an empty result or the target elements.

These are the extension methods:

public static class XElementExtensions
{
    public static XElement ElementOrDefault(this XElement element, XName name)
    {
        if (element == null)
            return null;

        return element.Element(name);
    }

    public static IEnumerable<XElement> ElementsOrEmpty(this XElement element, XName name)
    {
        if (element == null)
            return Enumerable.Empty<XElement>();

        return element.Elements(name);
    }
}

You can use them in this manner:

var query = theElement.ElementOrDefault("Blah")
                      .ElementOrDefault("Whatever")
                      .ElementsOrEmpty("Something");
if (query.Any())
    // do something
else
    // no elements

If you're not querying for ElementsOrEmpty and your last request is for ElementOrDefault you would check for null instead of using the Enumerable.Any method.