using System;

using System.Linq;

using System.Collections.Generic;

​

public static class ChunkWhileEnumerable

{

    public static IEnumerable<IList<T>> ChunkWhile<T>(

        this IEnumerable<T> enumerable,

        Func<IReadOnlyList<T>, T, bool> chunkPredicate)

    {

        // Would be better off using the enumerable's enumerator but I

        // can't remember the syntax for and logic rules for that at 6am.

        var chunk = new List<T>();

        foreach (var element in enumerable) {

            if (chunkPredicate(chunk, element)) {

                chunk.Add(element);

            } else {

                yield return chunk;

                chunk = new List<T> { element };

            }

        }

​

        if (chunk.Count > 0) {

            yield return chunk;

        }

    }                                                     

}

​

public class Program

{

    public static void Main()

    {

        var now = DateTime.UtcNow;

        var flights = new[] {

            new { DepartureDate = now.AddMinutes(2) },

            new { DepartureDate = now.AddMinutes(5) },

            new { DepartureDate = now.AddMinutes(15) },

            new { DepartureDate = now.AddMinutes(31) },

            new { DepartureDate = now.AddMinutes(45) },

            new { DepartureDate = now.AddMinutes(50) },

            new { DepartureDate = now.AddMinutes(61) },

            new { DepartureDate = now.AddMinutes(74) },

            new { DepartureDate = now.AddMinutes(75) },

        };

        var sorted = flights.OrderBy(d => d.DepartureDate);

        var chunks = sorted.ChunkWhile((chunk, f) => {

            var first = chunk.DefaultIfEmpty(f).First().DepartureDate;

            var span = f.DepartureDate.Subtract(first);

            return (span.TotalMinutes < 30);

        });

        foreach (var chunk in chunks) {

            Console.WriteLine("Chunk ");

            foreach (var flight in chunk) {

                Console.WriteLine(flight.DepartureDate);

            }

        }

    }

}