Runner run = new Runner();
       string filePath = "runners.xml"; //path
        XDocument xDoc = XDocument.Load(filePath);
        string userSelect = name;



        var averageAddDistancequery = xDoc.Descendants("User").Where(w => (string)w.Element("Name") == user).Select(s => new
        {
            add = s.Elements("Attempts").Where(w => (string)w.Element("Place").Value == "Paris").Select(t => t.Element("Distance").Value)
        }).ToList();

        if (averageAddDistancequery[0].add.Count() > 0)
        {
            var aa = averageAddDistancequery[0].add.Average(a => float.Parse(a));
            run.averageDistance = aa.ToString();
        }
        else
        {
           // nothing
        }

        var averageAdd2Distancequery = xDoc.Descendants("User").Where(w => (string)w.Element("Name") == userSelector).Select(s => new
        {
            add = s.Elements("Attempts").Where(w => (string)w.Element("Place").Value == "Madrid").Select(t => t.Element("Distance").Value)
        }).ToList();

        if (averageAdd2Distancequery[0].add.Count() > 0)
        {
            var aa = averageAdd2DistanceSubquery[0].add.Average(a => float.Parse(a));
            run.averageDistance2 = aa.ToString();
        }
        else
        {
           // nothing
        }



        xmlDoc.DocumentElement.SetAttribute("searching", user);
        XmlNodeList tests = xmlDoc.SelectNodes("//User[Name =/*/@searching]/Attempts");
        listBox1.Items.Clear();
        listBox1.Items.Add("Runners Name: " + user);
        listBox1.Items.Add("Overall  Distance in Paris: " + run.averageAdd);
        listBox1.Items.Add("Overall Distance in Madrid: " + run.averageSub);

Users>
    <User>
     <Name>David</Name>
      <Attempts>
       <Place>Paris</Place>
       <Date>3/29/2012</Date>
       <Distance>100</Distance>
     </Attempts>
     <Attempts>
      <Place>Madrid</Place>
      <Date>7/28/2012</Date>
      <Distance>100</Distance>
     </Attempts>
     <Attempts>
      <Place>Paris</Place>
      <Date>8/19/2012</Date>
      <Distance>60</Distance>
     </Attempts>
     <Attempts>
      <Place>Madrid</Place>
      <Date>9/29/2012</Date>
      <Distance>200</Distance>
    </Attempts>
   </User>
   <User>
    <Name>Lenny</Name>
     <Attempts>
      <Place>Paris</Place>
      <Date>9/29/2012</Date>
      <Distance>130</Distance>
     </Attempts>
  </User>
 </Users>

var userElement = xDox.Descendants("User")
                .SingleOrDefault(u => u.Element("Name").Value == "David");

if (userElement != null)
{
    var result = userElement.Descendants("Attempts")
        .Select(a => new
            {
                Place = a.Element("Place").Value,
                Date = DateTime.Parse(a.Element("Date").Value),
                Distance = int.Parse(a.Element("Distance").Value)
            })

        .Where(a => a.Date >= DateTime.Parse("3/29/2012")
                    && a.Date <= DateTime.Parse("8/29/2012"))

        .GroupBy(a => a.Place)
        .Select(g => new {Place = g.Key, Avg = g.Average(x => x.Distance)});
}

XElement x = XElement.Load("In.xml");
IFormatProvider f = new System.Globalization.CultureInfo("en-US");

DateTime bdate = DateTime.Parse("3/29/2012", f);
DateTime edate = DateTime.Parse("8/29/2012", f);
string username = "David";

var info = x.Elements("User")
            .Where(u => u.Element("Name").Value == username)
            .Select(u => new
{
  Name = u.Element("Name").Value,                   //user name
  AverageAttempts = u.Elements("Attempts")          //select user's attempts
                     .Where(a =>                    //filter by dates
                     {
                        DateTime d = DateTime.Parse(a.Element("Date").Value, f);
                        return d >= bdate && d <= edate;
                     })
                     .GroupBy(a => a.Element("Place").Value) //group by place
                     .Select(g => new         // create summary info by place
                     {
                        Place = g.Key,              //place
                        BeginDate = g.Elements("Date")
                                     .Select(d => DateTime.Parse(d.Value, f))
                                     .Min(),   //min date, i.e. first attempt
                        EndDate = g.Elements("Date")
                                   .Select(d => DateTime.Parse(d.Value, f))
                                   .Max(),   //max date, i.e. last attempt
                        Distance = g.Elements("Distance")//average distance
                                    .Average(d => decimal.Parse(d.Value))
                     })
})
.FirstOrDefault();

if(info!=null)
{
   Console.WriteLine(info.Name);
   foreach (var aa in info.AverageAttempts)
   {
       Console.WriteLine(string.Format("{0} [{1} - {2}]:t{3}",
                                       aa.Place,
                                       aa.BeginDate,
                                       aa.EndDate,
                                       aa.Distance));
   }
}

XElement root = XElement.Load(file);
XElement david = root.XPathElement("//User[Name={0}]", "David");
XElement[] attempts = david
         .XPath("Attempts[Date>={0} and Date<={1}]",
                new DateTime(2012, 3, 29), new DateTime(2012, 8, 29))
         .ToArray();