How to find gaps between multiple, variable DateRanges in C#?

Question

Hello, I'm doing an appointment finder, where you can input multiple users' appointments and it should find empty gaps in a list with multiple and variable DateRanges. The methods I wrote do unfortunately not work. How could I do this without a large library like TimePeriodLibrary.

This is the appointments collection:

List < Range > appointments = new List < Range > ();

// user 1
appointments.Add(new Range(new DateTime(2020, 8, 3, 0, 0, 0), new DateTime(2020, 8, 4 + 1, 0, 0, 0)));
appointments.Add(new Range(new DateTime(2020, 8, 7, 10, 0, 0), new DateTime(2020, 8, 7, 12, 0, 0)));

// user 2
appointments.Add(new Range(new DateTime(2020, 8, 3, 14, 0, 0), new DateTime(2020, 8, 3, 15, 30, 0)));
appointments.Add(new Range(new DateTime(2020, 8, 6, 0, 0, 0), new DateTime(2020, 8, 6 + 1, 0, 0, 0)));
appointments.Add(new Range(new DateTime(2020, 8, 6, 0, 0, 0), new DateTime(2020, 8, 6 + 1, 0, 0, 0)));

// user 3
appointments.Add(new Range(new DateTime(2020, 8, 3, 14, 0, 0), new DateTime(2020, 8, 3, 15, 30, 0)));
appointments.Add(new Range(new DateTime(2020, 8, 6, 0, 0, 0), new DateTime(2020, 8, 6 + 1, 0, 0, 0)));
appointments.Add(new Range(new DateTime(2020, 8, 6, 0, 0, 0), new DateTime(2020, 8, 6 + 1, 0, 0, 0)));

// ...

And this is my Range class:

class Range {
	private readonly DateTime _start;
	private readonly DateTime _end;

	public Range(DateTime start, DateTime end) {
		if (start.CompareTo(end) >= 0) {
			var temp = end;
			end = start;
			start = temp;
		}

		_start = start;
		_end = end;
	}

	public DateTime Start {
		get {
			return _start;
		}
	}

	public DateTime End {
		get {
			return _end;
		}
	}
}

Thanks for any help :)

Answer 1

Hi TheSteveXYZ,
In order to avoid misunderstandings, do you want to find out "gaps" time between the two time periods? 
Such as:
User1:

appointments.Add(new Range(new DateTime(2020, 8, 3, 0, 0, 0), new DateTime(2020 , 8, 5, 0, 0, 0)));

User2

appointments.Add(new Range(new DateTime(2020, 8, 7, 10, 0, 0), new DateTime(2020, 8, 7, 12, 0, 0)));

The result should be like this:"start time: 2020, 8, 5, 0, 0, 0  end time :2020, 8, 7, 10, 0, 0".

If so, there are some methods in this links you can refer to.
[How to get gap in date ranges from a period of time]
[Find Gap Date Ranges from two Set of Date Ranges C#]

If not, please explain in detail.
Best Regards,
Daniel Zhang

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Answer 2

Hi

What is your requirements can explain briefly

Thanks  and regards

Answer 3

Thank you.

I used the Extension method from your second link (https://stackoverflow.com/a/15452877/11304248 (can't hyperlink it because my account here is new)) and replaced the AddDays with AddMinutes to also search for gaps in days. 

I came up with the following class:

public static class DateRangeEnumerable
    {
        public static IEnumerable<DateTime> GetDates(this IEnumerable<DateRange> source)
        {
            var sortedSource = source.OrderBy(r => r.StartDate);

            foreach (var range in sortedSource)
            {
                var d = range.StartDate;
                while (d < range.EndDate)
                {
                    yield return d;
                    //d = d.AddDays(1);
                    d = d.AddMinutes(1);
                }
            }
        }

        public static IEnumerable<DateRange> GetRanges(this IEnumerable<DateTime> source)
        {
            var sortedSource = source.OrderBy(d => d);
            var enumerator = sortedSource.GetEnumerator();

            if (!enumerator.MoveNext())
                yield break;

            DateTime from = enumerator.Current;
            DateTime prev = from;

            while (true)
            {
                while (true)
                {
                    if (enumerator.MoveNext())
                    {
                        //if (enumerator.Current == prev.AddDays(1))
                        if (enumerator.Current == prev.AddMinutes(1))
                            prev = enumerator.Current;
                        else
                            break;
                    }
                    else
                    {
                        //yield return new DateRange(from, prev.AddDays(1));
                        yield return new DateRange(from, prev.AddMinutes(1));
                        yield break;
                    }

                }

                //yield return new DateRange(from, prev.AddDays(1));
                yield return new DateRange(from, prev.AddMinutes(1));

                from = enumerator.Current;
                prev = enumerator.Current;
            }
        }
    }

And it works fine with the rest of my code.