LINQ query — Data aggregation (Group Adjacent)

Question

Let\'s take a class called Cls:

public class Cls
{
    public int SequenceNumber { get; set; }
    public int Value { get; set; }
}

Answer 1

Untested dark magic follows. The imperative version seems like it would be easier in this case.

IEnumerable data = ...;
var query = data
    .GroupBy(x => x.Value)
    .Select(g => new
    {
        Value = g.Key,
        Sequences = g
            .OrderBy(x => x.SequenceNumber)
            .Select((x,i) => new
            {
                x.SequenceNumber,
                OffsetSequenceNumber = x.SequenceNumber - i
            })
            .GroupBy(x => x.OffsetSequenceNumber)
            .Select(g => g
                .Select(x => x.SequenceNumber)
                .OrderBy(x => x)
                .ToList())
            .ToList()
    })
    .SelectMany(x => x.Sequences
        .Select(s => new { First = s.First(), Last = s.Last(), x.Value }))
    .OrderBy(x => x.First)
    .ToList();