Linq学习笔记二(Linq to sql 增删改查)

1.接上篇http://www.cnblogs.com/greatverve/archive/2010/05/12/1733513.html
在Northwind下新建表t_User
ID,             int,主键，自增。
UserName,  varchar(50)
Pwd,           varchar(50)

2.从服务器资源管理器中把t_User拖到Northwind.dbml中。
即生成orm映射。

3.增删改查的代码参考下面的Linq3();

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

using System.Data.Common;
using System.Collections.Generic;

namespace FirstLinq
{
    public partial class _Default : System.Web.UI.Page
    {
        NorthwindDataContext ctx = new NorthwindDataContext("Data Source=ZHANGSHUQIANG;Initial Catalog=Northwind;Persist Security Info=True;User ID=sa;Password=sa");
        protected void Page_Load(object sender, EventArgs e)
        {
            Linq1();
            Linq2();
            Linq3();
        }
        /// <summary>
        /// 增删改查
        /// </summary>
        private void Linq3()
        {
            //增
            t_User user = new t_User();
            user.UserName = "大气象";
            user.Pwd = "123456";
            ctx.t_User.InsertOnSubmit(user);//以前的方法是Add();
            ctx.SubmitChanges();

            //改
            //参考这样的语法string s = (from a in ctx.Customers select a).Single(a => a.ID == 2);
            t_User userUpdate = ctx.t_User.SingleOrDefault(t_User => t_User.ID == 2);//Single与SingleOrDefault没区别
            userUpdate.UserName = "大气象1";
            ctx.SubmitChanges();

            //删
            t_User userDelete = (from userinfo in ctx.t_User where userinfo.ID == 1 select userinfo).FirstOrDefault();
            if (userDelete != null)
            {
                ctx.t_User.DeleteOnSubmit(userDelete);
                ctx.SubmitChanges();
            }
        }
        /// <summary>
        /// 熟悉Linq to sql语法
        /// </summary>
        private void Linq2()
        {
            Customers customer = new Customers();

            //执行普通的sql语句，查询CustomerID="ANATR"的记录
            IEnumerable<Customers> customers = ctx.ExecuteQuery<Customers>("select * from Customers where CustomerID='ANATR'");
            customer = customers.First();
            Response.Write(customer.CustomerID);

            //使用Linq查询单条记录
            var cus = from c in ctx.Customers where c.CustomerID.Equals("ANATR") select c;
            customer = cus.First();
            Response.Write(customer.CompanyName);

            //查询结果集，语法：from 临时表名 in 表集合 orderby 临时表名.字段名 升级序 select 临时表名
            gdvCustomers.DataSource = from cust in ctx.Customers where cust.CustomerID != "ANATR" orderby cust.CompanyName descending select cust;
            gdvCustomers.DataBind();
        }
        /// <summary>
        /// 熟悉一下linq语法，变量的定义类似js，无须声明类型。
        /// </summary>
        private void Linq1()
        {
            var age = 29;
            var username = "greatverve";
            var userlist = new[] { "a", "b", "c" };
            foreach (var user in userlist)
            {
                Response.Write(user);
            }
        }
    }
}

参考：
http://www.cnblogs.com/webabcd/archive/2007/10/18/928353.html
http://www.cnblogs.com/lovecherry/archive/2007/08/16/858009.html