Analyze-File.cs

using System;
using System.Diagnostics;
using System.IO;
using System.Linq;

namespace FileAnalyzer
{
    public class Record
    {
        public DateTime Start => DateTime.Parse(_line.Split(' ')[0]);

        public DateTime End => DateTime.Parse(_line.Split(' ')[1]);
        public long Id => long.Parse(_line.Split(' ')[2]);

        public TimeSpan Duration => End - Start;

        private readonly string _line;

        public Record(string line)
        {
            _line = line;
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            AppDomain.MonitoringIsEnabled = true;
            var sp = Stopwatch.StartNew();

            var summary = from line in File.ReadAllLines(args[0])
                let record = new Record(line)
                group record by record.Id
                into g
                select new
                {
                    Id = g.Key,
                    Duration = TimeSpan.FromTicks(g.Sum(r => r.Duration.Ticks))
                };

            using (var output = File.CreateText("summary.txt"))
            {
                foreach (var entry in summary)
                {
                    output.WriteLine($"{entry.Id:D10} {entry.Duration:c}");
                }
            }

            Console.WriteLine($"Took: {sp.ElapsedMilliseconds:#,#} ms and allocated " +
                              $"{AppDomain.CurrentDomain.MonitoringTotalAllocatedMemorySize / 1024:#,#} kb " +
                              $"with peak working set of {Process.GetCurrentProcess().PeakWorkingSet64 / 1024:#,#} kb");

        }
    }
}