XML node Latest timestamp C#

Question

I need to only print the same employee once and check if its the latest timestamp. I need employee id only once but the latest timestamp of it.

This is my result so far, printing same id with different timestamps (example):

1 2015-03-16T21:32:30
1 2015-03-16T21:33:30
2 2015-03-16T21:32:30
3 2015-03-16T21:32:30
2 2015-03-16T21:33:30

This is what my code looks like right now.

  static void Main(string[] args)
        {
            XElement xelement = XElement.Load("data.xml");
            IEnumerable<XElement> employees = xelement.Elements();
            Console.WriteLine("List of Employee and latest timestamp:");
            foreach (var employee in employees)
            {
                Console.WriteLine("{0} has Employee ID {1}",
                    employee.Element("Employee").Value,
                    employee.Element("ChangeTimeStamp").Value);
            }
            Console.ReadKey();
        }

To be clear i would like my result to be :

1 2015-03-16T21:33:30
2 2015-03-16T21:33:30
3 2015-03-16T21:32:30

Answer 1

You need to group your employee nodes by the value of Employee element like this:

XElement xelement = XElement.Load("data.xml");
var employees = xelement.Elements()
            .Select(e => new 
            {
                Name = e.Element("Employee").Value,
                ChangeTimestamp = DateTime.Parse(e.Element("ChangeTimestamp").Value)
            })
            .GroupBy(e => e.Name)
            .Select( g => new 
            {
                Name = g.Key,
                ChangeTimestamp = g.Max(e => e.ChangeTimestamp)
            });

Now, when you iterate you should have the proper values

foreach(var employee in employees)
{
    Console.WriteLine("{0} {1}", employee.Name, employee.ChangeTimestamp);
}

Edit I

To remove the other elements except the ones with the last version you should filter them and remove each one from their parent. The code should look something like this:

XElement xelement = XElement.Load("data.xml");
xelement.Elements()
    .GroupBy(e => e.Element("Employee").Value)
    .SelectMany(g =>
    {
        var maxDate = g.Max( e => DateTime.Parse(e.Element("ChangeTimestamp").Value));
        return g.Where(e => DateTime.Parse(e.Element("ChangeTimestamp").Value) != maxDate);
    })
    .ToList()
    .ForEach(e=>e.Remove());

This, of course is not the optimal solution but it gives you a hint in the right direction. Adjust it to fit your needs.

Edit II

The file from the paste bin has 3 different employees and not 3 different ChangeTimestamps for one single employee. I've tried the following snippet and it worked:

XDocument doc = XDocument.Load(@"path");
doc.Root.Elements("Employee")
    .GroupBy(e => e.Element("Employee").Value)
    .SelectMany(g=>
    {
        return g.OrderByDescending(e => DateTime.Parse(e.Element("ChangeTimeStamp").Value))
            .Skip(1);
    })
    .ToList()
    .ForEach(e=>e.Remove());