using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Diagnostics;

public class Program

{

    private static Random random = new Random((int)DateTime.Now.Ticks);

    public static void Main()

    {

        Console.WriteLine("Hello World");

        IList<Employee> employee = GetEmployees();

        Stopwatch sw = new Stopwatch();

        sw.Start();

        var t1 = employee.Where(x=>x!=null).Where(x=>x.EmpID>10).Where(x=>x.Rank>2).Select(x=>x.EmpName).ToList();

        sw.Stop();

        var tm1 = sw.ElapsedTicks;

        sw.Restart();

        var t2 = employee.Where(x=>x!=null && x.EmpID>10 && x.Rank>2).Select(x=>x.EmpName).ToList();

        sw.Stop();

        var tm2 = sw.ElapsedTicks;

        Console.WriteLine(tm1);

        Console.WriteLine(tm2);

    }

    private static IList<Employee> GetEmployees()

    {

        var arrNames = new string[1000];

        for(var i=0; i<arrNames.Length; i++)

        {

            arrNames[i] = RandomString(8);

        }

        var res = new List<Employee>(arrNames.Length);

        foreach(var s in arrNames)

        {

            res.Add(new Employee() {EmpID = random.Next(0, arrNames.Length), EmpName=s, EmpMarks=random.Next(0, 100), Rank=random.Next(0, 10)});

        }

        return res;

    }

    private static string RandomString(int length)

    {

        const string pool = "abcdefghijklmnopqrstuvwxyz0123456789";

        var builder = new StringBuilder();

​

        for (var i = 0; i < length; i++)

        {

            var c = pool[random.Next(0, pool.Length)];

            builder.Append(c);

        }

​

        return builder.ToString();

    }

}

​

public class Employee {

   public int EmpID { get; set; }

   public string EmpName { get; set; }

   public int EmpMarks { get; set; }

   public int Rank { get; set; }

}