using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;

public class MainClass {
    public static void Main() {
        string[] presidents = {"G", "H", "a", "H", "over", "Jack"};

        string name = presidents.Last(p => p.StartsWith("H"));
        Console.WriteLine(name);
    }
}

    

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

public class MainClass{
   public static void Main(){
            int[] numbers = { 1, 3, 5, 7, 9 };
            var query = numbers.FirstOrDefault(n => n % 2 == 0);
            Console.WriteLine("The first even element in the sequence");
            Console.Write(query);
            Console.WriteLine("The last odd element in the sequence");
            query = numbers.LastOrDefault(n => n % 2 == 1);
            Console.Write(query);
   }
}

    

   
 

using System;
delegate int NumericSequence();

class Test {
    static NumericSequence Natural() {
        return () => { int seed = 0; return seed++; };
    }

    static void Main() {
        NumericSequence natural = Natural();
        Console.WriteLine(natural());
        Console.WriteLine(natural());
    }
}

    

   
 

using System;
delegate int Transformer(int i);

class Test {
    static void Main() {
        Transformer square = x => x * x;
        Console.WriteLine(square(3));    // 9
    }
}

    

   
 
using System;
delegate int NumericSequence();

class Test {
    static NumericSequence Natural() {
        int seed = 0;
        return () => seed++;

    }

    static void Main() {
        NumericSequence natural = Natural();
        Console.WriteLine(natural());
        Console.WriteLine(natural());
    }
}

    

using System;
using System.Linq;
using System.Linq.Expressions;

class Program {
static void Main(string[] args) {
Expression> isOddExpression = i => (i & 1) == 1;
ParameterExpression param = Expression.Parameter(typeof(int), “i”);
Expression> isOdd =
Expression.Lambda>(
Expression.Equal(
Expression.And(
param,
Expression.Constant(1, typeof(int))),
Expression.Constant(1, typeof(int))),
new ParameterExpression[] { param });

Func isOddCompiledExpression = isOddExpression.Compile();
for (int i = 0; i < 10; i++) { if (isOddCompiledExpression(i)) Console.WriteLine(i + " is odd"); else Console.WriteLine(i + " is even"); } } } [/csharp]

   
 
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 Role {
    int _id;
    string role;

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

    public string Role {
        get { return role; }
        set { role = 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"}
            };
        List<Role> roles = new List<Role> {
              new Role  { ID = 1, Role = "Manager" },
              new Role  { ID = 2, Role = "Developer" }
            };
        var query = from p in people
                    join r in roles on p.IDRole equals r.ID
                    select p;
    }
}