using System;

using System.Collections.Generic;

using System.Linq;

using Newtonsoft.Json;

​

class Program

{

    static void Main(string[] args)

    {

        var data = new List<List<IndexData>>

        {

            new List<IndexData>

            {

                new IndexData { Name = "ESG Sustainability", Date = new DateTime(2022, 01, 31), ReturnRate = 0 },

                new IndexData { Name = "S&P BSE 100 Total Return Index", Date = new DateTime(2022, 01, 31), ReturnRate = 0 },

                new IndexData { Name = "S&P BSE Sensex Total Return Index", Date = new DateTime(2022, 01, 31), ReturnRate = 0 },

                new IndexData { Name = "NIFTY 100 Total Return Index", Date = new DateTime(2022, 01, 31), ReturnRate = 0 },

                new IndexData { Name = "NIFTY 50 Total Return Index", Date = new DateTime(2022, 01, 31), ReturnRate = 0 }

            },

            new List<IndexData>

            {

                new IndexData { Name = "ESG Sustainability", Date = new DateTime(2022, 02, 01), ReturnRate = -0.08 },

                new IndexData { Name = "S&P BSE 100 Total Return Index", Date = new DateTime(2022, 02, 01), ReturnRate = -0.04 },

                //new IndexData { Name = "S&P BSE Sensex Total Return Index", Date = new DateTime(2022, 02, 01), ReturnRate = -0.01 },

                new IndexData { Name = "NIFTY 100 Total Return Index", Date = new DateTime(2022, 02, 01), ReturnRate = -0.02 },

                new IndexData { Name = "NIFTY 50 Total Return Index", Date = new DateTime(2022, 02, 01), ReturnRate = -0.10 }

            }

        };

​

        var groupedByDate = data.SelectMany(list => list)

                                .GroupBy(index => index.Date)

                                .Select(group =>{

                                    var a =group.ToDictionary(index => index.Name, index => index.ReturnRate.ToString());

                                    a["date"] = group.Key.ToString("yyyy-MM-dd");

                                        return a;

                                }

                                    );

​

        string json = JsonConvert.SerializeObject(groupedByDate, Formatting.Indented);

        Console.WriteLine(json);

    }

}

​

class IndexData

{

    public string Name { get; set; }

    public DateTime Date { get; set; }

    public double ReturnRate { get; set; }

}

​