Specific Elements from an XML document

Question

I have the following XML:

<?xml version="1.0" encoding="utf-8" ?>
<catalog>
  <books>
<book id="bk101"> 
  <author id="1">Gambardella, Matthew</author>
  <title>XML Developer's Guide</title>
  <genre>Computer</genre>
  <cover-price>
    <price>
        <country>US</country>
        <amount>44.95</amount>
    </price>
    <price>
        <country>UK</country>
        <amount>39.99</amount>
    </price>
  </cover-price>
  <unit-price>
    <price>
        <country>US</country>
        <amount>25.00</amount>
    </price>
    <price>
        <country>UK</country>
        <amount>20.00</amount>
    </price>
  </unit-price>
  <publish_date>2000-10-01</publish_date>
   <description> An in-depth look at creating applications with XML.</description>
</book>
<book id="bk102">
  <author id="2">Ralls, Kim</author>
  <title>Midnight Rain</title>
  <genre>Fantasy</genre>
  <cover-price>
    <price>
        <country>US</country>
        <amount>5.95</amount>
    </price>
    <price>
        <country>UK</country>
        <amount>3.99</amount>
    </price>
  </cover-price>
  <unit-price>
    <price>
        <country>US</country>
        <amount>2.50</amount>
    </price>
    <price>
        <country>UK</country>
        <amount>2.00</amount>
    </price>
  </unit-price>
  <publish_date>2000-12-16</publish_date>
  <description> A former architect battles corporate zombies,an evil sorceress, and her own childhood to become
queen of the world.</description>
</book>
<book id="bk103">
  <author id="3">Corets, Eva</author>
  <title>Maeve Ascendant</title>
  <genre>Fantasy</genre>
  <cover-price>
    <price>
        <country>US</country>
        <amount>5.95</amount>
    </price>
    <price>
        <country>UK</country>
        <amount>3.99</amount>
    </price>
  </cover-price>
  <unit-price>
    <price>
        <country>US</country>
        <amount>2.50</amount>
    </price>
    <price>
        <country>UK</country>
        <amount>2.00</amount>
    </price>
  </unit-price>
    <publish_date>2000-11-17</publish_date>
    <description>After the collapse of a nanotechnology society in England, the young survivors lay the foundation for
a new society. </description>
  </book>

<book id="bk104">
    <author id="4">Corets, Eva</author>
    <title>Oberon's Legacy</title>
    <genre>Fantasy</genre>
  <cover-price>
    <price>
        <country>US</country>
        <amount>5.95</amount>
    </price>
    <price>
        <country>UK</country>
        <amount>3.99</amount>
    </price>
  </cover-price>
  <unit-price>
    <price>
        <country>US</country>
        <amount>2.50</amount>
    </price>
    <price>
        <country>UK</country>
        <amount>2.00</amount>
    </price>
  </unit-price>
    <publish_date>2001-03-10</publish_date>
    <description>In post-apocalypse England, the mysterious agent known only as Oberon helps to create a new life for
 the inhabitants of London. Sequel to Maeve Ascendant.</description>

  </book>

<book id="bk105">
    <author id="5">Corets, Eva</author>
    <title>The Sundered Grail</title>
    <genre>Fantasy</genre>
  <cover-price>
    <price>
        <country>US</country>
        <amount>5.95</amount>
    </price>
    <price>
        <country>UK</country>
        <amount>3.99</amount>
    </price>
  </cover-price>
  <unit-price>
    <price>
        <country>US</country>
        <amount>2.50</amount>
    </price>
    <price>
        <country>UK</country>
        <amount>2.00</amount>
    </price>
  </unit-price>
    <publish_date>2001-09-10</publish_date>
    <description>The two daughters of Maeve, half-sisters, battle one another for control of England. Sequel to
Oberon's Legacy.</description>

  </book>
  </books>
</catalog>

I can use the following to select a specific book

var selectedBook = from r in document.Descendants("book").Where
                                   (r=>(string)r.Attribute("id")=="bk102")
                        select new
                        {
                            Author = r.Element("author").Value,
                            Title = r.Element("title").Value,
                            Genere = r.Element("genre").Value,
                            Price = r.Element("price").Value,
                            PublishDate = r.Element("publish_date").Value,
                            Description = r.Element("description").Value,

                        };

How do I then select that book's cover-price amount for the US? Every combination I've tried just returns all four of the amount fields

Answer 1

• Currently you're trying to fetch a price element directly under book , so that's not going to work to start with.
• Next you want to only select the price element with the right country sub-element
• Finally, you don't want the value of the price element, you want the value of its amount child element - and I'd suggest getting that as a decimal rather than as a string

So that means instead of this:

Price = r.Element("price").Value

You want something like:

Price = (decimal) r.Element("cover-price")
                   .Elements("price")
                   .Single(p => (string) p.Element("country") == "US")
                   .Element("amount")

That will still fail if there aren't any price elements with the right country. You could use this instead to obtain an appropriate decimal? :

Price = (decimal?) r.Element("cover-price")
                    .Elements("price")
                    .SingleOrDefault(p => (string) p.Element("country") == "US")
                    ?.Element("amount")

Answer 2

You're close

var selectedBook = from r in document.Descendants("book").Where
                                   (r=>(string)r.Attribute("id")=="bk102")
                        select new
                        {
                            Author = r.Element("author").Value,
                            Title = r.Element("title").Value,
                            Genere = r.Element("genre").Value,
                            Price = r.Element("price").Value,
                            PublishDate = r.Element("publish_date").Value,
                            Description = r.Element("description").Value,
                            USPrice = r.Element("cover-price") 
                                       .Descendants("country")
                                       .Where(c => (string)c == "US"))
                                       .Select(c => (decimal)c.Parent.Element("amount"))
                                       .First()
                        };