Csharp/CSharp Tutorial/LINQ/Projection

Projection Creates New Objects

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

    class Customer
    {
        public string ID { get; set; }
        public string City { get; set; }
        public string Country { get; set; }
        public string Region { get; set; }
        public decimal Sales { get; set; }
        public override string ToString()
        {
            return "ID: " + ID + " City: " + City + " Country: " + Country + " Region: " + Region + " Sales: " + Sales;
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            List<Customer> customers = new List<Customer> {
              new Customer { ID="A", City="New York", Country="USA", Region="North America", Sales=9999},
              new Customer { ID="R", City="Beijing", Country="China", Region="Asia", Sales=9000 },
              new Customer { ID="T", City="Lima", Country="Peru", Region="South America", Sales=2002 }
           };
            var queryResults =
                from c in customers
                where c.Region == "Asia"
                select new { c.City, c.Country, c.Sales }
               ;
            foreach (var item in queryResults)
            {
                Console.WriteLine(item);
            }
        }
    }

Projection Linq

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ruponentModel;
    public class Person
    {
        public int Age { get; set; }
        public string Name { get; set; }
        List<Person> friends = new List<Person>();
        public List<Person> Friends
        {
            get { return friends; }
        }
        public Person()
        {
        }
        public Person(string name)
        {
            Name = name;
        }
    }
    class Projection
    {
        static void Main()
        {
            List<Person> family = new List<Person>                 
            {
                new Person {Name="H", Age=31},
                new Person {Name="J", Age=31},
                new Person {Name="T", Age=4},
                new Person {Name="W", Age=1}
            };
            var converted = family.ConvertAll(delegate(Person person)
                { return new { person.Name, IsAdult = (person.Age >= 18) }; }
            );
            foreach (var person in converted)
            {
                Console.WriteLine("{0} is an adult? {1}",
                                  person.Name, person.IsAdult);
            }
        }
    }

Projection Operators: do calculation in select statement

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
public class MainClass {
    public static void Main() {
        int[] numbers = { 5, 4, 1, 3, 9};
        var numsPlusOne =
            from n in numbers
            select n + 1;
        Console.WriteLine("Numbers + 1:");
        foreach (var i in numsPlusOne) {
            Console.WriteLine(i);
        }
    }
}