public void EndExperiment(string experimentName, string alwaysUseOption)
{
var xml = Load();
var experiment = xml.Root.Elements("Experiment").Single(exp => exp.Attribute("Name").Value == experimentName);
if (experiment.Attribute("Ended") != null)
return;
experiment.Add(new XAttribute("Ended", UtcNow));
experiment.Add(new XAttribute("AlwaysUseOption", alwaysUseOption));
Save(xml);
}