How to collapse data in C# using Linq?

Question

C++ / C#

There is a Json - in which something like this comes in

{
  'orders' : [ 
    {
      id: 1,
      sku: 'AR',
      sum: 100
    },
    {
      id: 2,
      sku: 'PR',
      sum: 200
    },
    { 
      id: 1,
      sku: 'VR',
      sum: 150
    },
  ]
}

if the id's are the same, sum should be summed, and sku should be in the form of an array

Answer 1

It is not very clear what kind of array you want to get, but if, by analogy with summation, string concatenation is performed, then, for example, like this:

class Program
    {
        static void Main(string[] args)
        {
            List<Order> orders = new List<Order>()
            {
                new Order()
                {
                    id = 1,
                    sku = "AR",
                    sum = 100
                },
                new Order()
                {
                    id = 2,
                    sku = "PR",
                    sum = 200
                },
                new Order()
                {
                    id = 1,
                    sku = "VR",
                    sum = 150
                }
            };

            var groupedOrders = orders.GroupBy(el => el.id)
                .Select(el => new Order()
                {
                    id = el.Key,
                    sum = el.Sum(s => s.sum),
                    sku = String.Join(String.Empty, el.Select(str => str.sku))
                });
           
        }
    }

    public class Order
    {
        public int id;
        public string sku;
        public int sum;
    }

Answer 2

It is not clear what the array should be for the Sku field, but without it it will look something like this:

class Program
{
  static void Main(string[] args)
  {
    string rawJson = File.ReadAllText("data.json"); // for example
    OrderCollection orders = JsonConvert.DeserializeObject<OrderCollection>(rawJson);

    foreach (var item in orders.Orders.GroupBy(x => x.Id))
    {
      Console.WriteLine($"Order id: {item.Key}, sum: {item.Sum(x => x.Sum)}");
    }
  }
}

class OrderCollection
{
  public List<Order> Orders { get; set; }
}

class Order
{
  public int Id { get; set; }
  public string Sku { get; set; }
  public int Sum { get; set; }
}