using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var data = new List<Sample>

        {

            new Sample {id = 1, date = "02-10", clicks = 1, views = 2},

            new Sample {id = 1, date = "02-10", clicks = 2, views = 2},

            new Sample {id = 1, date = "02-19", clicks = 3, views = 2},

            new Sample {id = 2, date = "02-11", clicks = 4, views = 2},

            new Sample {id = 2, date = "02-11", clicks = 5, views = 2},

        };

​

        var result = data.GroupBy(i => new { i.id, i.date })

            .Select(g => new Sample

            {

                id = g.Key.id,

                date = g.Key.date,

                clicks = g.Sum(i => i.clicks),

                views = g.Sum(i => i.views),

            });

        // print result

        result.ToList().ForEach(i => Console.WriteLine($"id={i.id},date={i.date},clicks={i.clicks},views={i.views}"));

    }

    class Sample

    {

        public int id { get; set; }

        public string date { get; set; }

        public int clicks { get; set; }

        public int views { get; set; }

    }

}