using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;
using System.Linq;
using System.Reflection;

class Person {
    int _id;
    int _idRole;
    string _lastName;
    string _firstName;

    public int ID {
        get { return _id; }
        set { _id = value; }
    }

    public int IDRole {
        get { return _idRole; }
        set { _idRole = value; }
    }

    public string LastName {
        get { return _lastName; }
        set { _lastName = value; }
    }

    public string FirstName {
        get { return _firstName; }
        set { _firstName = value; }
    }
}
class Program {
    static void Main(string[] args) {
        List<Person> people = new List<Person> {
              new Person  { ID = 1, IDRole = 1, LastName = "A", FirstName = "B"},
              new Person  { ID = 2, IDRole = 2, LastName = "G", FirstName = "T"},
              new Person  { ID = 3, IDRole = 2, LastName = "G", FirstName = "M"},
              new Person  { ID = 4, IDRole = 3, LastName = "C", FirstName = "G"}
            };

        var query = people.Where((p, index) => p.IDRole == index);
    }
}

    

   
 
using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
public class MainClass {
    public static void Main() {

        string[] presidents = {"Ad", "Ar", "Bu", "B", "C", "C"};

        string president = presidents.Where(p => p.StartsWith("Ad")).First();

        Console.WriteLine(president);
    }
}

    

   
 

using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
public class MainClass {
    public static void Main() {


        string[] presidents = {"AA", "A", "AAA", "B", "Ca", "C"};

        IEnumerable<string> items = presidents.Where(p => p.StartsWith("A"));

        foreach (string item in items)
            Console.WriteLine(item);

    }
}

    

   
 


using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
public class MainClass {
    public static void Main() {
        string[] presidents = {"AAAA", "aaaa", "bacDert", "B1234", "Carter"};

        IEnumerable<string> items = presidents.Where(s => Char.IsLower(s[4]));

        Console.WriteLine("After the query.");

        foreach (string item in items)
            Console.WriteLine(item);

    }
}

    

   
 


using System;
using System.Linq;

public class MainClass {
    public static void Main() {
        string[] greetings = { "hello world", "hello LINQ", "hello" };

        var items =
         from s in greetings
         where s.EndsWith("LINQ")
         select s;

        foreach (var item in items)
            Console.WriteLine(item);
    }
}

    

   
 

using System;
using System.Collections.Generic;
using System.Linq;
public class MainClass {
    public static void Main() {

        IEnumerable<char> query = "Not what you might expect";

        query = query.Where(c => c != &#039;a&#039;);
        query = query.Where(c => c != &#039;e&#039;);
        query = query.Where(c => c != &#039;i&#039;);
        query = query.Where(c => c != &#039;o&#039;);
        query = query.Where(c => c != &#039;u&#039;);

        foreach (char c in query) Console.Write(c); 
    }
}

    

   
 


using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
public class MainClass {
    public static void Main() {

        string[] names = { "A1", "B123", "C123123", "E", "W" };

        IEnumerable<string> sequence = names
         .Where(n => n.Length < 6)
         .Select(n => n);

        foreach (string name in sequence) {
            Console.WriteLine("{0}", name);
        }
    }
}