using System;

using System.Linq;

using MoreLinq;

new[] {

    new Availability

    {

        Accessibility = 1,

        RoomTypeId = "12345",

        Rate = 50,

        DateFrom = new DateTime(2022, 01, 01),

        DateTo = new DateTime(2022, 01, 01)

    },

    new Availability

    {

        Accessibility = 1,

        RoomTypeId = "12345",

        Rate = 50,

        DateFrom = new DateTime(2022, 01, 02),

        DateTo = new DateTime(2022, 01, 02)

    },

    new Availability

    {

        Accessibility = 1,

        RoomTypeId = "12345",

        Rate = 100,

        DateFrom = new DateTime(2022, 01, 04),

        DateTo = new DateTime(2022, 01, 04)

    },

    new Availability

    {

        Accessibility = 6,

        RoomTypeId = "12345",

        Rate = 100,

        DateFrom = new DateTime(2022, 01, 05),

        DateTo = new DateTime(2022, 01, 05)

    },

    new Availability

    {

        Accessibility = 6,

        RoomTypeId = "12345",

        Rate = 100,

        DateFrom = new DateTime(2022, 01, 6),

        DateTo = new DateTime(2022, 01, 06)

    }

}

.GroupBy(x => new { x.RoomTypeId, x.Rate, x.Accessibility })

.SelectMany(groupedAvails => groupedAvails

    .OrderBy(avail => avail.DateFrom)

    .Segment((curr, prev, _) => prev.DateTo.AddDays(1) != curr.DateFrom)

    .Select(consecutiveAvails => new Availability {

        Accessibility = consecutiveAvails.First().Accessibility,

        RoomTypeId = consecutiveAvails.First().RoomTypeId,

        Rate = consecutiveAvails.First().Rate,

        DateFrom = consecutiveAvails.First().DateFrom,

        DateTo = consecutiveAvails.Last().DateTo

    }))

.ForEach(mergedAvail => Console.WriteLine($"{mergedAvail.RoomTypeId} {mergedAvail.Rate} {mergedAvail.Accessibility} {mergedAvail.DateFrom.ToShortDateString()} {mergedAvail.DateTo.ToShortDateString()}"));

public class Availability {

    public int Accessibility { get; init; }

    public string RoomTypeId { get; init; }

    public int Rate { get; init; }

    public DateTime DateFrom { get; init; }

    public DateTime DateTo { get; init; }

}