public class MemberHierarchyCTE
{
   public int ChildId { set; get; }
   public int? ParentId { set; get; }
}

var memberHierarchyCte =
                    context.CreateLinqToDbContext().GetCte<MemberHierarchyCTE>(memberHierarchy =>
                    {
                        return
                            (
                                from member in context.Members
                                select new MemberHierarchyCTE
                                {
                                    ChildId = member.MemId,
                                    ParentId = member.RecommendedBy
                                }
                            )
                            .Concat
                            (
                                from member in context.Members
                                from hierarchy in memberHierarchy
                                            .InnerJoin(hierarchy => member.MemId == hierarchy.ParentId)
                                select new MemberHierarchyCTE
                                {
                                    ChildId = hierarchy.ChildId,
                                    ParentId = member.RecommendedBy
                                }
                            );
                    });

WITH [memberHierarchy] ([ChildId], [ParentId])
AS
(
    SELECT
        [member_1].[MemId],
        [member_1].[RecommendedBy]
    FROM
        [Members] [member_1]
    UNION ALL
    SELECT
        [hierarchy_1].[ChildId],
        [member_2].[RecommendedBy]
    FROM
        [Members] [member_2]
            INNER JOIN [memberHierarchy] [hierarchy_1] ON [member_2].[MemId] = [hierarchy_1].[ParentId]
)

dotnet add package linq2db.EntityFrameworkCore

LinqToDB.EntityFrameworkCore.LinqToDBForEFTools.Initialize();
LinqToDB.Data.DataConnection.TurnTraceSwitchOn();

var runningTotalCountForEachYear = context.Bookings
             .Select(booking => new
             {
                 booking.StartTime.Year,
                 RunningTotalCount =
                     Sql.Ext.Count(booking.StartTime)
                             .Over()
                             .OrderBy(booking.StartTime.Year)
                             .ToValue()
             })
             .OrderBy(result => result.Year)
             .Distinct()
             .ToLinqToDB()
             .ToList();

SELECT DISTINCT
    DatePart(year, [booking].[StartTime]),
    COUNT([booking].[StartTime]) OVER(ORDER BY DatePart(year, [booking].[StartTime]))
FROM
    [Bookings] [booking]
ORDER BY
    DatePart(year, [booking].[StartTime])