using System;

using System.Collections.Generic;

using System.Linq;                  

public class Program

{

    class Package

{

    public string Company { get; set; }

    public double Weight { get; set; }

    public long TrackingNumber { get; set; }

}

    public static void Main()

    {

            List<Package> packages =

        new List<Package>

            { new Package { Company = "Coho Vineyard", 

                  Weight = 25.2, TrackingNumber = 89453312L },

              new Package { Company = "Lucerne Publishing", 

                  Weight = 18.7, TrackingNumber = 89112755L },

              new Package { Company = "Wingtip Toys", 

                  Weight = 6.0, TrackingNumber = 299456122L },

              new Package { Company = "Contoso Pharmaceuticals", 

                  Weight = 9.3, TrackingNumber = 670053128L },

              new Package { Company = "Wide World Importers", 

                  Weight = 33.8, TrackingNumber = 4665518773L } };

​

    // Create a Lookup to organize the packages. 

    // Use the first character of Company as the key value.

    // Select Company appended to TrackingNumber 

    // as the element values of the Lookup.

    var lookup =

        packages

        .ToLookup(p => Convert.ToChar(p.Company.Substring(0, 1)),

                  p => p.Company + " " + p.TrackingNumber);

        Console.WriteLine(Newtonsoft.Json.JsonConvert.SerializeObject(lookup));

    }

}