Trying to understand how to conditionally write out element/attributes with LIINQToXML - linq

Question

This is the first time that I created a XML document using LINQToXML.
I am trying to understand how can I conditionally create attributes(or elements) when creating my document?
In this example a given car may/may not have a feature to it, so in that case I would not want to create that element, I also may have certain attributes in the feature node that could be missing. How could I handle these scenarios?
XDocument xDoc = new XDocument(
new XElement("root",
new XElement("NodeA"),
new XElement("Cars",
from p in listCars
select new XElement("Car", new XAttribute("name", p.CarName),
new XElement("Feature", new XAttribute("door", p.Door), new XAttribute("model", p.Model))
)
)
)
);
Desired result #1 (All features are missing for a given car):
<root>
<NodeA />
<Cars>
<Car name="Honda">
<Feature door="4" model="Accord" />
</Car>
<Car name="Ford" />
</Cars>
</root>
Desired result #2 (Some features could exist)
<root>
<NodeA />
<Cars>
<Car name="Honda">
<Feature door="4" model="Accord" />
</Car>
<Car name="Ford">
<Feature model="Focus" />
</Car>
</Cars>
</root>

Answer 1

2 seperate solutions in here. Either use a method to create the features node, or do it all in one:
static void Main(string[] args)
{
var listCars = new List<Car>();
listCars.Add(new Car { CarName = "test 1", Door = "0", Model = "" });
listCars.Add(new Car { CarName = "test 2", Door = "", Model = "" });
listCars.Add(new Car { CarName = "test 3", Door = "0", Model = "0" });
XDocument xDoc2 = new XDocument(
new XElement("root",
new XElement("NodeA"),
new XElement("Cars",
from p in listCars
select new XElement("Car",
new XAttribute("name", p.CarName),
p.Door != "" || p.Model != "" ?
new XElement("Feature",
p.Door != "" ? new XAttribute("door", p.Door) : null,
p.Model != "" ? new XAttribute("model", p.Model) : null) : null
)
)
)
);
XDocument xDoc = new XDocument(
new XElement("root",
new XElement("NodeA"),
new XElement("Cars",
from p in listCars
select new XElement("Car",
new XAttribute("name", p.CarName),
CreateFeature(p)
)
)
)
);
}
static XElement CreateFeature(Car p)
{
var el = new XElement("Feature",
p.Door != "" ? new XAttribute("door", p.Door) : null,
p.Model != "" ? new XAttribute("model", p.Model) : null);
return !el.Attributes().Any() ? null : el;
}

Answer 2

If you supply null instead of an element, it will be ignored, so you can use constructs like the following.
p.CarName != null ? new XAttribute("name", p.CarName) : null
If you're using C# 6, you can use null propagation.