Question

I have an xml document like this:

<?xml version="1.0" encoding="utf-8" ?>
<demographics>
    <country id="1" value="USA">
        <state id ="1" value="California">
            <city>Long Beach</city>
            <city>Los Angeles</city>
            <city>San Diego</city>
        </state>
        <state id ="2" value="Arizona">
            <city>Tucson</city>
            <city>Phoenix</city>
            <city>Tempe</city>
        </state>
    </country>
    <country id="2" value="Mexico">
        <state id ="1" value="Baja California">
            <city>Tijuana</city>
            <city>Rosarito</city>            
        </state>
    </country>
</demographics> 

How do I setup LINQ queries for doing things like:
1. Get All Countries
2. Get All States in a Country
3. Get All Cities inside a state of a paricular country ?

I gave it a try and I am kind of confused when to use Elements[“NodeName”] and Descendants etc. I know I am not the brightest XML guy around. Is the format of the XML file even correct for simple traversal?

Answer 1

To load the document from a file:

XDocument document = XDocument.Load("input.xml");

To get all the countries’ names:

IEnumerable<string> countries = document
    .Descendants("country")
    .Select(element => element.Attribute("value").Value);

To get all the states that are inside the country “USA”:

IEnumerable<string> states = document
    .Descendants("country")
    .Where(element => element.Attribute("value").Value == "USA")
    .Elements("state")
    .Select(element => element.Attribute("value").Value);

To get all the cities inside USA/California:

IEnumerable<string> cities = document
    .Descendants("country")
    .Where(element => element.Attribute("value").Value == "USA")
    .Elements("state")
    .Where(element => element.Attribute("value").Value == "California")
    .Elements("city")
    .Select(element => element.Value);

You might also want to look at XPath queries (you need using System.XML.XPath):

IEnumerable<string> cities = document
    .XPathSelectElements("/demographics/country[@value='USA']/state[@value='California']/city")
    .Select(element => element.Value);