Question

I’m trying to build an XML file that reads the content to put inside from a list:

List<Snack> trashFoods

When I create the XML file, it would be something like this:

XDocument doc = new XDocument(
    new XDeclaration("1.0", "utf-8", "yes"),
    new XComment(""),
    new XElement("Snacks",
    trashFoods.Select(snack =>
        new XElement("Type", snack.Type),
        new XElement("Name", snack.Name)
    ),
)

What I want to, and I am unable to do is something like putting conditionals inside the construction of the XML file. Similar to this:

XDocument doc = new XDocument(
    new XDeclaration("1.0", "utf-8", "yes"),
    new XComment(""),
    new XElement("Snacks",
    trashFoods.Select(snack =>
        new XElement("Type", snack.Type),
        if(snack.Type == "Doritos")
        {
            new XElement("GotSauce", snack.Sauce),
        }
        new XElement("Name", snack.Name)
    ),
)

Is this such a thing even possible with LINQ to XML even if the syntax is not the same?

Answer 1

LINQ to XML objects are not immutable, so you can rewrite your declarative code into imperative one using Add():

XDocument doc = new XDocument(
    new XDeclaration("1.0", "utf-8", "yes"),
    new XComment("")
);

XElement snacks = new XElement("Snacks");

foreach (var snack in trashFoods)
{
    snacks.Add(new XElement("Type", snack.Type));

    if(snack.Type == "Doritos")
        snacks.Add(new XElement("GotSauce", snack.Sauce));

    snacks.Add(new XElement("Name", snack.Name));
}

doc.Add(snacks);

It’s not very pretty, but it work. Another approach would be to extract the conditional code into a method using yield return:

XDocument doc = new XDocument(
    new XDeclaration("1.0", "utf-8", "yes"),
    new XComment(""),
    new XElement("Snacks",
        trashFoods.Select(snack => GetSnackChildren(snack))));

…

IEnumerable<XElement> GetSnackChildren(Snack snack)
{
    yield return new XElement("Type", snack.Type);
    if(snack.Type == "Doritos")
    {
        yield return new XElement("GotSauce", snack.Sauce);
    }
    yield return new XElement("Name", snack.Name);
}

This looks better, but it splits code that probably should be together.