简单的LINQ例子 学习初期

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

namespace LQ
{
    [Table(Name = "Customers")]      //这里是将数据库中的Customers表映射到Customer类上
    public class Customer
    {
        [Column]   //顾名思义   列
        public string CustomerID { get; set; }
        [Column]
        public string City { get; set; }

        public override string ToString()
        {
            return CustomerID + "\t" + City;
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            //NumQuery();
            ObjectQuery();
            Console.Read();
        }

        static IEnumerable<Customer> CreateCustomers()
        {
            return new List<Customer>
            {
                new Customer{CustomerID="ALFKI",City="Berlin"},
                new Customer{CustomerID="BONAP",City="Marseille"},
                new Customer{CustomerID="CONSH",City="London"},
                new Customer{CustomerID="EASTC",City="London"},
                new Customer{CustomerID="FRANS",City="Torino"},
                new Customer{CustomerID="LONEP",City="Portland"},
                new Customer{CustomerID="NORTS",City="London"},
                new Customer{CustomerID="THEBI",City="Portland"}
            };
        }

        static void ObjectQuery()
        {
            //DataContext   这个东西是LINQ最基本也是最重要的东西  是LINQ to SQL的入口点  详细的请查询MSDN
            var db = new DataContext(@"Data Source=SHNI010\SQLEXPRESS;Initial Catalog=Northwind;Integrated Security=True");

            //var results = from c in CreateCustomers()
            //              where c.City == "London"
            //              select c.CustomerID;
            //LINQ的查询语句
            var results = from c in db.GetTable<Customer>()
                          where c.City == "London"
                          select c;
            db.Log=Console.Out;
            foreach (var c in results)  //循环结果集
            {
                Console.WriteLine("{0}\t{1}",c.CustomerID,c.City);
            }
            Console.Read();
        }

　　　　//下面这个方法是LINQ对数组的查询  可见LINQ对很多通用
        static void NumQuery()
        {
            var numbers = new int[] { 1,4,9,16,25,36};
            var evenNumbers = from p in numbers
                              where (p % 2) == 0
                              select p;
            Console.WriteLine("Result:");
            foreach (var val in evenNumbers)
            {
                Console.WriteLine(val);
            }
            Console.Read();
        }
    }
}