Question

I have a List<MyObject> …
MyObject has a propert called LineId (integer)…

So, I need separate all consecutive LineId in List …

Example :

List<MyObject> :

LineId =1
LineId =1
LineId =1
LineId =2
LineId =1
LineId =2

The result must be 4 separeted lists:

LineId =1
LineId =1
LineId =1
-------------
LineId =2
-------------
LineId =1
-------------
LineId =2

So, I must separate all consecutive LineId …

Is there an easy way to do that using Linq?

Thanks

Answer 1

This looks ugly but the idea is clear and I think it works:

var agg = list.Aggregate(
    new List<List<Line>>(),
    (groupedLines, line) => {
        if (!groupedLines.Any()) {
            groupedLines.Add(new List<Line>() { line });
        }
        else {
            List<Line> last = groupedLines.Last();
            if (last.First().LineId == line.LineId) {
                last.Add(line);
            }
            else {
                List<Line> newGroup = new List<Line>();
                newGroup.Add(line);
                groupedLines.Add(newGroup);
            }
        }
        return groupedLines;
    }
);

Here I am assuming that you have:

class Line { public int LineId { get; set; } }

and

List<Line> list = new List<Line>() {
    new Line { LineId = 1 },
    new Line { LineId = 1 },
    new Line { LineId = 1 },
    new Line { LineId = 2 },
    new Line { LineId = 1 },
    new Line { LineId = 2 }
};

Now if I execute

foreach(var lineGroup in agg) {
    Console.WriteLine(
        "Found {0} consecutive lines with LineId = {1}",
        lineGroup.Count,
        lineGroup.First().LineId
    );
    foreach(var line in lineGroup) {
        Console.WriteLine("LineId = {0}", line.LineId);
    }
}

I see:

Found 3 consecutive lines with LineId = 1
LineId = 1
LineId = 1
LineId = 1
Found 1 consecutive lines with LineId = 2
LineId = 2
Found 1 consecutive lines with LineId = 1
LineId = 1
Found 1 consecutive lines with LineId = 2
LineId = 2

printed on the console.