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

Here is an implementation without any helper methods:

var grp = 0;
var results =
from i
in
input.Zip(
    input.Skip(1).Concat(new [] {input.Last ()}),
    (n1, n2) => Tuple.Create(
        n1, (n2.Value == n1.Value) ? grp : grp++
    )
)
group i by i.Item2 into gp
select new {SequenceNumFrom = gp.Min(x => x.Item1.SequenceNumber),SequenceNumTo = gp.Max(x => x.Item1.SequenceNumber), Value = gp.Min(x => x.Item1.Value)};

The idea is:

• Keep track of your own grouping indicator, grp.
• Join each item of the collection to the next item in the collection (via Skip(1) and Zip).
• If the Values match, they are in the same group; otherwise, increment grp to signal the start of the next group.