Additional square brackets in Linq result-CodePudding

In my DB, I have the following data:

track_id, point_id, latd, lond
A,1,12,100
A,2,13,101
B,1,10,90
B,2,13,90

I am trying to generate a IEnumerable<object[]> as follow:

[[12, 100],[13, 101]], [[10, 90],[13, 90]]

Which will be used in a multilinestring Geojson:

This is what I have tried:

var multiTrackList = _context.tracks
    .GroupBy(g => g.track_id)
    .Select(s => new object[] {
        _context.tracks
        .Where(w => w.track_id == s.Key)
        .OrderBy(o => o.track_id).ThenBy(o => o.date).ThenBy(o => o.time)
        .Select(e => new object[] { e.lond.Value, e.latd.Value }).ToList()
    });

but it keeps returning:

[[[12, 100],[13, 101]]], [[[10, 90],[13, 90]]]

with extra unneeded square brackets. I don't see what I am doing wrong. Please help.

CodePudding user response：

I'm not sure what you're trying to accomplish with all the grouping and ordering, but you're doing too many selects on your data source, generating [2][2][2] arrays. Maybe this will point you in the right direction:

context _context = new();
_context.tracks = new();
_context.tracks.Add(new track("A", 12, 100));
_context.tracks.Add(new track("A", 13, 101));
_context.tracks.Add(new track("B", 10, 90));
_context.tracks.Add(new track("B", 13, 90));


var multiTrackList = _context.tracks
.GroupBy(g => g.track_id) //grouping
.SelectMany(e => e.Where(x => x.track_id == e.Key)) //selection where track_id equals Keys on the grouped elements
.OrderBy(o => o.track_id) //ordering, I removed the date and time for simplicity
.Select(y => new object[2] { y.latd, y.lond }) //then you can generate your 2 positions array
.ToList(); //finally you can convert the IEnumerable into a List, or whatever you need
Console.Write(JsonConvert.SerializeObject(multiTrackList)); //"[[12,100],[13,101],[10,90],[13,90]]"

CodePudding user response：

Thanks to @james-braz and after editing his answer, I was able to get the correct linq query:

var multiTrackList = _context.tracks
                             .GroupBy(g => g.track_id ) //grouping
                             .Select(e => 
                                    e.Where(x => x.cruise_id == e.Key) //selection where track_id equals Keys on the grouped elements
                                    .OrderBy(o => o.date).ThenBy(o => o.time) //ordering, I removed the date and time for simplicity
                                    .Select(y => new object[2] { y.latd, y.lond })//then you can generate your 2 positions array
                             ).ToList(); //finally you can convert the IEnumerable into a List, or whatever you need

I obtain the correct output ([[12,100],[13,101],[10,90],[13,90]]), I can use to update the coordinates property of my multilinestring GeoJSON