using System;

using System.Collections;

using System.Collections.Generic;

using System.IO;

using System.Reflection;

using System.Text.RegularExpressions;

using System.Linq;

namespace codeTest

{

    class Program

    {

        static void Main(string[] args)

        {

            //linq : Lauage Intergarted Query

            //继承IEnumerable的类，都可以使用linq

            //Linq to sql,Linq to xml,Linq to DataSet,Linq to objects

            //linq语句在具体调用时，才会执行 toList() Count()

            List<Customer> Customers = new List<Customer>();

            Customers.Add(new Customer() { CustomerName = "Li1", CityID =  });

            Customers.Add(new Customer() { CustomerName = "Li2", CityID =  });

            Customers.Add(new Customer() { CustomerName = "Li3", CityID =  });

            Customers.Add(new Customer() { CustomerName = "Li4", CityID =  });

            List<City> Citys = new List<City>();

            Citys.Add(new City() { CityID = , CityName = "北京" });

            Citys.Add(new City() { CityID = , CityName = "上海" });

            Citys.Add(new City() { CityID = , CityName = "广州" });

            Citys.Add(new City() { CityID = , CityName = "深圳" });

            #region 简单查询

            //1.Query systax

            var query = from c in Customers

                        where c.CityID %  ==

                        orderby c.CityID descending

                        select c;

            foreach (var item in query)

            {

                Console.WriteLine("{0},{1}", item.CustomerName, item.CityID);

            }

            Console.WriteLine();

            //2.Method systax

            var query2 = Customers.Where(c => c.CityID %  == ).OrderByDescending(c => c.CityID);

            foreach (var item in query2)

            {

                Console.WriteLine("{0},{1}", item.CustomerName, item.CityID);

            }

            #endregion

            #region Group

            Console.WriteLine("queryGroup");

            //1.Query systax

            var queryGroup = from c in Customers

                             group c by c.CityID;

            foreach (var group in queryGroup)

            {

                Console.WriteLine("{0}", group.Key);

                foreach (var item in group)

                {

                    Console.WriteLine("{0},{1}", item.CustomerName, item.CityID);

                }

            }

            Console.WriteLine();

            //2.Method systax

            var queryGroup2 = Customers.GroupBy(c => c.CityID);

            foreach (var group in queryGroup2)

            {

                Console.WriteLine("{0}", group.Key);

                foreach (var item in group)

                {

                    Console.WriteLine("{0},{1}", item.CustomerName, item.CityID);

                }

            }

            #endregion

            #region into

            Console.WriteLine("into");

            //1.Query systax

            var queryGroupinto = from c in Customers

                                 group c by c.CityID into cGroup

                                 where cGroup.Count() >

                                 select new { CityID = cGroup.Key, Cout = cGroup.Count() };

            foreach (var group in queryGroupinto)

            {

                Console.WriteLine("{0},{1}", group.CityID,group.Cout);

            }

            Console.WriteLine();

            //2.Method systax

            var queryGroupinto2 = Customers.GroupBy(c => c.CityID).

                Where(cGroup => cGroup.Count() > ).

                Select(cGroup => new { CityID = cGroup.Key, Cout = cGroup.Count() });

            foreach (var group in queryGroupinto2)

            {

                Console.WriteLine("{0},{1}", group.CityID, group.Cout);

            }

            #endregion

            #region join

            Console.WriteLine("join");

            //1.Query systax

            var queryJoin = from c in Customers

                            join ci in Citys on c.CityID equals ci.CityID

                            select new { CustomerName = c.CustomerName, c.CityID, ci.CityName };

            foreach (var item in queryJoin)

            {

                Console.WriteLine("{0},{1},{2}", item.CustomerName, item.CityID,item.CityName);

            }

            Console.WriteLine();

            //2.Method systax

            var queryJoin2 = Customers.Join(Citys,

                c => c.CityID,

                ci => ci.CityID,

                (c, ci) => new { CustomerName = c.CustomerName, c.CityID, ci.CityName });

            foreach (var item in queryJoin2)

            {

                Console.WriteLine("{0},{1},{2}", item.CustomerName, item.CityID, item.CityName);

            }

            #endregion

            Console.ReadLine();

        }

        class Customer

        {

            public string CustomerName { get; set; }

            public int CityID { get; set; }

        }

        class City

        {

            public int CityID { get; set; }

            public string CityName { get; set; }

        }

    }

}