My attempt to solve Lunchtime LINQ Challenge part1 https://www.markheath.net/post/lunchtime-linq-challenge

LINQchallenges1.cs

//challeng 1
string names = "Davis, Clyne, Fonte, Hooiveld, Shaw, Davis, Schneiderlin, Cork, Lallana, Rodriguez, Lambert";
var team = names.Split(',').Select((player, index) => (index + 1) + ". " + player.Trim()).Aggregate((curr, next) => curr + ", " + next);

//challenge 2 (see answer)
string playersData = "Jason Puncheon, 26/06/1986; Jos Hooiveld, 22/04/1983; Kelvin Davis, 29/09/1976; Luke Shaw, 12/07/1995; " +
                "Gaston Ramirez, 02/12/1990; Adam Lallana, 10/05/1988";

var players = playersData.Split(';').Select(player => (Name: player.Trim().Substring(0, player.IndexOf(',') - 1), DoB: DateTime.ParseExact(player.Substring(player.IndexOf(',') + 1).Trim(), "dd/MM/yyyy", CultureInfo.InvariantCulture))).Select(x => new { x.Name, x.DoB, Age = DateTime.Now.Year - x.Item2.Year }).OrderBy(x => x.Age).ToList();

//challenge 3 (see answer)
string durations = "4:12,2:43,3:51,4:29,3:24,3:14,4:46,3:25,4:52,3:27";
var timeOfAll = durations.Split(',').Select(dur =>
            {
                var time = dur.Split(':');
                return TimeSpan.FromMinutes(int.Parse(time[0])) + TimeSpan.FromSeconds(int.Parse(time[1]));
            }).Aggregate((cur, next) => cur + next);

//challenge 4  (see answer)
int[] pts = new int[] { 0, 1, 2 };
string grid = (from x in pts from y in pts select x + "," + y).Aggregate((a, b) => a + " " + b);

//challenge 5
string durations = "00:45,01:32,02:18,03:01,03:44,04:31,05:19,06:01,06:47,07:35";
var timeSpans = durations.Split(',').Select(x =>
        {
            var span = x.Split(':');
            var min = span[0];
            var sec = span[1];
            return TimeSpan.FromMinutes(double.Parse(min)) + TimeSpan.FromSeconds(double.Parse(sec));
        });
var lengths = timeSpans.Zip(timeSpans.Prepend(TimeSpan.FromSeconds(0)), (x, y) => x - y);

//challenge 6
string input = "2,5,7-10,11,17-18";
List<int> nums = new List<int>();

foreach (var item in input.Split(','))
{
    if (item.Contains('-'))
    {
        var bounds = item.Split('-');
        var lower = int.Parse(bounds[0]);
        var upper = int.Parse(bounds[1]);
        for (int i = lower; i <= upper; i++)
        {
            nums.Add(i);
        }
    }
    else
        nums.Add(int.Parse(item));
}

//answers
https://www.markheath.net/post/lunchtime-linq-challenge-answers