using System;

using System.Linq;

using System.Collections.Generic;

​

//LINQ

public class IntroToLINQ

{        

    public static void Main()

    {

        // The Three Parts of a LINQ Query:

        //  1. Data source.

        int[] numbers = new int[7] { 0, 1, 2, 3, 4, 5, 6 };

​

        // 2. Query creation.

        // numQuery is an IEnumerable<int>

        var numQuery =

            from num in numbers

            where (num % 2) == 0

            select num;

        var numQuery3 =

            (from num in numbers

                where (num % 2) == 0

                select num).ToArray();

        // 3. Query execution.

        foreach (int num in numQuery)

        {

            Console.Write("{0,1} ", num);

        }

        Console.WriteLine();

        Console.WriteLine(numQuery.GetType());

        Console.WriteLine(numQuery3.GetType());

        Customer cust1 = new Customer("London","Jack","Wong");

        //Console.WriteLine(cust1);

        Customer cust2 = new Customer("London","Jack","Zhong");

        Customer cust3 = new Customer("London","Jack","Long");

        Customer cust4 = new Customer("New York","Jack","Chong");

        Customer cust5 = new Customer("New York","Jack","Li");

        Database db = new Database();

        db.Add(cust1,cust2,cust3,cust4,cust5);

        Console.WriteLine("Using delegate...");

        foreach (Customer result in db.FindAll(x => x.City == "New York"))

        {

            Console.WriteLine(result);

        }

        var customerQuery = 

            from cust in db.customers

            where cust.City == "London"

            select cust;

        Console.WriteLine("Using Linq Query");

        foreach (Customer customer in customerQuery)

        {

            Console.WriteLine(customer);    

        }

    }

}

​

public class Customer

{

    public string City;

    public string LastName;

    public string FirstName;

​

    public Customer(string c, string fn, string ln)

    {

        this.City = c;

        this.FirstName = fn;

        this.LastName = ln;

    }

    public override string ToString(){

        return String.Format("{0} {1} from {2}",this.FirstName,this.LastName,this.City);

    }

}

​

​

public class Database

{

    public List<Customer> customers;

    public Database()

    {

        customers = custList;

    }

    private List<Customer> custList = new List<Customer>();

    public int count

    {

        get{ return custList.Count();}

    }

    public void Add(params Customer[] custL)

    {

        foreach (Customer cust in custL)

            custList.Add(cust);

    }

    public void Remove(params Customer[] custL)

    {

        foreach (Customer cust in custL)

            if (custList.Contains(cust))

                custList.Remove(cust);

            else

                Console.WriteLine("Customer not found");

    }

    public List<Customer> FindAll(Predicate<Customer> p)

    {

        return custList.FindAll(p);

    }

    public int RemoveAll(Predicate<Customer> p)

    {

        return custList.RemoveAll(p);

    }

}

​

​