using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        TimeRange query = new TimeRange() { Start = new DateTime(2020, 1, 1, 0, 0, 0), End = new DateTime(2020, 1, 31, 23, 59, 59) };

        List<TimeRange> exclusionRanges = new List<TimeRange>();

        TimeRange er1 = new TimeRange() { Start = new DateTime(2019, 12, 28, 0, 0, 0), End = new DateTime(2020, 1, 6, 0, 0, 0) };

        TimeRange er2 = new TimeRange() { Start = new DateTime(2020, 1, 12, 0, 0, 0), End = new DateTime(2020, 1, 16, 0, 0, 0) };

        TimeRange er3 = new TimeRange() { Start = new DateTime(2020, 1, 28, 0, 0, 0), End = new DateTime(2020, 1, 29 , 0, 0, 0) };

​

        exclusionRanges.Add(er1);

        exclusionRanges.Add(er3);

        exclusionRanges.Add(er2);

​

        var ranges = query.excludeRanges(exclusionRanges);

        foreach(var rv in ranges)

        {

            Console.WriteLine(rv.ToString());

        }

    }

     public class TimeRange

    {

        public DateTime Start { get; set; }

        public DateTime End { get; set; }

         public TimeRange(){

         }

         public TimeRange(DateTime start, DateTime end)

         {

             Start = start;

             End = end;

         }

​

        public IEnumerable<TimeRange> excludeRanges(IEnumerable<TimeRange> ranges)

        {

            var min = Start;

            var returnRanges = new List<TimeRange>();

​

            var orderedRanges = ranges.OrderBy(r => r.Start);

​

            if (!ranges.Any()) { return new List<TimeRange>() { this }; }

​

            if (orderedRanges.First().Start <= Start && orderedRanges.First().End > Start) { min = orderedRanges.First().End; }

​

            foreach (var tr in orderedRanges)

            {

                returnRanges.Add(new TimeRange(min, tr.Start));

                min = tr.End;

            }

​

            if (returnRanges.Last().End < End)

            {

                returnRanges.Add(new TimeRange(orderedRanges.Last().End, End));

            }

​

            return returnRanges;

        }

         public override string ToString()

        {

            return $"{Start} - {End}";

        }

    }

}