Question

I’m stumped yet again by XDocument. I’m trying to extract the value of the temperature element (12 in this example) when the class attribute has a value=”high” (and “low”)

A subset of my XML:

<forecastGroup>
    <forecast>
      <temperatures>
          <textSummary>Low plus 2. High 12.</textSummary>
          <temperature unitType="metric" units="C" class="high">12</temperature>
          <temperature unitType="metric" units="C" class="low">2</temperature>
      </temperatures>
    </forecast>
    ...etc.
    <forecast>
          <temperature unitType="metric" units="C" class="high">15</temperature>
          <temperature unitType="metric" units="C" class="low">3</temperature>
    </forecast>
<forecastGroup>

Code so far:

XDocument loaded = XDocument.Parse(strInputXML);
foreach (var forecast in loaded.Descendants("forecastGroup").Elements("forecast"))
{
   //existing code doing stuff here using the XDocument loaded
   High = "this is where I'm lost";
}

I’ve seemingly tried every combinations of trying to select Elements, Attributes, and Descendants”, but I’m at a loss.

Answer 1

To extract the high inside your loop, you could use the line

var high = (int)forecast.Element("temperatures")
                        .Elements("temperature")
                        .Where(temp => temp.Attribute("class").Value == "high")
                        .First();

Of course, you could use Linq-to-XML to simply project the entire XML tree into an appropriate object graph without explicitly taking it apart in a loop, but you should be able to progress your way towards that. It may end up looking something like

var forecasts = from forecast in loaded.Descendants("forecast")
                let temps = forecast.Element("temperatures")
                let high = temps.Elements("temperature").Where(t => t.Attribute("class").Value == "high").First()
                let low = temps.Elements("temperature").Where(t => t.Attribute("class").Value == "low").First()
                select new
                {
                    Temperatures = new
                    {
                        Summary = temps.Element("textSummary").Value,
                        High = new
                        {
                            UnitType = high.Attribute("unitType").Value,
                            Units = high.Attribute("units").Value,
                            Value = (int)high
                        },
                        Low = new
                        {
                            UnitType = low.Attribute("unitType").Value,
                            Units = low.Attribute("units").Value,
                            Value = (int)low
                        },
                    }
                };