Question

Lets say you have an XML like like this:

 <data>
  <messages>
   <message name="Person" id="P">
    <field name="FirstName" required="Y" />
    <field name="LastName" required="Y" />
    <field name="Sex" required="N" />
   </message>
   <message name="Car" id="C">
    <field name="Make" required="Y" />
    <field name="Model" required="Y" />
    <field name="Year" required="N" />
   </message>
  </messages>
 </data>

Using Linq, how would you get a list of all required field names for Person?

I just started playing with LINQ/XML today this is about as far as Ive gotten.

    var q = from c in loaded.Descendants("field")
            where (string)c.Attribute("required") == "Y" &&
            // how to check the parent node (message) has an attribute (id="P")           
            select (string)c.Attribute("name");

    foreach (string name in q)
        Console.WriteLine(name);

Answer 1

This answer is totally wrong considering the questioner changed his xml. Should I delete this.

var q = from c in loaded.Descendants("field")
            where (string)c.Attribute("required") == "Y" &&
                    c.Parent.Attribute("id").Value == "P"
            select (string)c.Attribute("name");

Adding the Xml I used because there is some confusion over the right solution.

XDocument loaded = XDocument.Parse(@"
<message name=""Person"" id=""P"">
    <field name=""FirstName"" required=""Y"" /> 
    <field name=""LastName"" required=""Y"" />
    <field name=""Sex"" required=""N"" />
    <message name=""Car"" id=""C"">
        <field name=""Make"" required=""Y"" />
        <field name=""Model"" required=""Y"" />
        <field name=""Year"" required=""N"" />
    </message>
</message>");