using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        //creating a list of students...

        List<Students> StudentData = new List<Students>

        {

                new Students{ID= 101,Name = "Sony", Marks = 780},

                new Students{ID = 102, Name = "Rohan", Marks = 890},

                new Students{ID=103,Name = "Shiva", Marks = 896}

        };

        //using linq query convert the list into Dictionary....

        Dictionary<int,string> results = StudentData.ToDictionary(x => x.ID, x=> x.Name);

        Console.WriteLine("Converting List of items to Dictionary");

        foreach(KeyValuePair<int,string> d in results)

        {

            Console.WriteLine(d.Key + "  " + d.Value);

        }

        //converting student class into dictionary value...

        Dictionary<int,Students> sresult = StudentData.ToDictionary(x => x.ID);

        //above lambda expression x => x.ID is dictionary key, x => x is dictionary value.....

        Console.WriteLine();

        Console.WriteLine("Converting whole student class as a dictionationay value...");

        foreach(KeyValuePair<int,Students> d in sresult)

            Console.WriteLine(d.Key + " " + d.Value.Name + " " + d.Value.Marks);

        ///ToList and ToArray also works in the same way....

        int[] Numbers = new int[]{12,34,45,67,56,23,43,21,10};

        List<int> numresult = Numbers.Where(x => x>20).ToList();

        Console.WriteLine();

        Console.WriteLine("Converting data to List");

        foreach(int n in numresult)

            Console.WriteLine(n);

    }

}

public class Students

{

    public int ID{get;set;}

    public string Name{get;set;}

    public int Marks{get;set;}

}