How to conditionally read elements in LINQToXML - linq

Question

How would I go about creating my desired list by using LINQToXml?
I am close with both attempts so far. I should be able to do this without creating to separate queries right?
This is my XML:
<main>
<cars>
<car name="Honda">
<feature door="4" name="Accord" />
<feature door="2" name="Civic"/>
<feature door="4" name="CRV"/>
</car>
<car name="Ford"/>
<car name="Kia"/>
<car name="Subaru">
<feature door="4" name="Outback"/>
<feature door="4" name="Legacy"/>
</car>
</cars>
</main>
Attempt #1
This will return the first car with feature.
var listCars = (from c in doc.Root.Descendants("cars")
select new Car
{
Model = (p.Element("car") != null) ? p.Element("car").Attribute("name").Value : null,
Door = (p.Element("car") != null) ? p.Element("car").Attribute("door").Value : null,
Name = p.Attribute("name").Value
}).ToList();
Attempt #2
This will return all of the cars that have features
Ford and Kia would be missing
var cars = from c in doc.Root.Descendants("cars")
select c;
var listPermissions = (from c in cars.Descendants("car")
let cName = p.Parent.Attribute("name").Value
select new Car
{
Model = p.Attribute("name").Value,
Door = p.Attribute("door").Value,
Name = pgn
}).ToList();
What I am trying to do is to create a list of cars that look like:
Honda, 4, Accord
Honda, 2, Civic
Honda, 4, CRV
Ford, null, null
Kia, null, null
Subaru, 4, Outback
Subaru, 4, Legacy

Answer 1

You can do this by using a LEFT JOIN in LINQ as outlined on 101 LINQ Samples.
var makes =
(from doc in document.Root.Descendants("cars").Descendants("car")
join f in document.Root.Descendants("cars").Descendants("car").Descendants("feature")
on doc.Attribute("name").Value.ToLowerInvariant() equals f.Parent.Attribute("name").Value.ToLowerInvariant() into ps
from f in ps.DefaultIfEmpty()
select new
{
Model = doc.Attribute("name").Value,
Door = f == null ? string.Empty : f.Attribute("door").Value,
Name = f == null ? string.Empty : f.Attribute("name").Value
})
.ToList();