Linq查询以获取Json结果

Question

I'm trying to do a linq query that will return Json results for a jquery chart.

I have a list of Movement objects:

MovementId
MovedFrom
MovedTo  

So example data would be:

1, Sydney, Melbourne
2, Dallas, Boston
3, Boston, Dallas
4, Boston, Dallas
5, Sydney, Brisbane

I'm trying to get the results like this:

categories: Boston, Brisbane, Dallas, Melbourne, Sydney (note in alphabetical order)
leaving: 2, 0, 1, 0, 2
arriving: 1, 1, 2, 1, 0

So 2 people have left Boston, and 1 has arrived

What I've tried so far:

I can get the categories by using the following line query to get the distinct values and merging them:

return Json(new
{
    categories = movements
            .Select(m => new[] { m.MovedFrom, m.MovedTo })
            .SelectMany(i => i)
            .Distinct()
            .ToList()
});

However, I can't seem to get an OrderBy working to put these in order.

I haven't found out how to get the leaving and arriving values. Was thinking of a foreach that puts them into an array, but was hoping there was a nice way to do it via linq

Answer 1

I'm not sure if this is what you want. This is not the best approach but can you try this?

                        movements
                        .Select(m => new[] { m.MovedFrom, m.MovedTo })
                        .SelectMany(i => i)
                        .Distinct()
                        .OrderBy(e => e)
                        .Select(e => new
                        {
                            categories = e,
                            leaving = movements.Count(x => x.MovedFrom == e),
                            arriving = movements.Count(x => x.MovedTo == e)
                        });

Answer 2

This should do it:

var cities = movements
    .Select(m => new[] { m.MovedFrom, m.MovedTo })
    .SelectMany(n => n)
    .Distinct()
    .OrderBy(n => n)
    .Select(n => new
    {
        category = n,
        leaving = movements.Count(m => m.MovedFrom == n),
        arriving = movements.Count(m => m.MovedTo == n)
    })
    .ToList();

var result = new
{
    categories = cities.Select(c => c.category).ToList(),
    leaving = cities.Select(c => c.leaving).ToList(),
    arriving = cities.Select(c => c.arriving).ToList()
};

return Json(result);

Fiddle: https://dotnetfiddle.net/eLCcJt

Answer 3

I'm not sure if there are any shorter way than this but this will yield you the output you desire. First create a view model class for your chart view.

            List<MovementObject> movements = new List<MovementObject>()
            {
                new MovementObject() { MovementId = 1, MovedFrom = "Sydney", MovedTo = "Melbourne"},
                new MovementObject() { MovementId = 2, MovedFrom = "Dallas", MovedTo = "Boston"},
                new MovementObject() { MovementId = 3, MovedFrom = "Boston", MovedTo = "Dallas"},
                new MovementObject() { MovementId = 4, MovedFrom = "Boston", MovedTo = "Dallas"},
                new MovementObject() { MovementId = 5, MovedFrom = "Sydney", MovedTo = "Brisbane"},
            };

            var categories = movements
            .Select(m => new[] { m.MovedFrom, m.MovedTo })
            .SelectMany(i => i)
            .Distinct()
            .ToList();

            MovementChartViewModel viewModel = new MovementChartViewModel();

            foreach(var category in categories.OrderBy(category => category)) //For alphabetical order
            {
                viewModel.Categories.Add(category);
                viewModel.Leaving.Add(movements.Where(move => move.MovedFrom == category).Count());
                viewModel.Arriving.Add(movements.Where(move => move.MovedTo == category).Count());
            }
            return Json(new { viewModel });

Models:

        public class MovementChartViewModel
        {
            public MovementChartViewModel()
            {
                Categories = new List<string>();
                Leaving = new List<int>();
                Arriving = new List<int>();
            }

            public List<string> Categories { get; set; }
            public List<int> Leaving { get; set; }
            public List<int> Arriving { get; set; }
        }

        public class MovementObject
        {
            public int MovementId {get;set;}
            public string MovedFrom {get;set;}
            public string MovedTo { get; set; }  
        }