[转]MVC 经验总结_EF

var s1 = context.Student.Where(o => o.ID > 0 && o.Name != "")
.OrderByDescending(o => o.ID)
.OrderBy(o => o.Name)
.Select(o => new { o.Name, o.Class });
s1 = from s in context.Student
where s.ID > 0 && s.Name != ""
orderby s.ID descending, s.Name ascending
select new { s.Name, s.Class };

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

namespace ConsoleEFApplication2
{
class Program
{
static void Main(string[] args)
{
StudyDBEntities context = new StudyDBEntities();
/*
// 增
Student s1 = new Student();
s1.Name = "张三";
s1.Class = "101班";
context.Student.Add(s1);
context.SaveChanges();
*/
/* 跟踪数据库操作为：
INSERT [Student]([Name], [Class]) VALUES ('李四','103班')
SELECT [ID] FROM [Student] WHERE @@ROWCOUNT > 0 AND [ID] = scope_identity()
*/
/*
// 删
int id = 1;
var s3 = from s in context.Student
where s.ID == id
select s;
context.Student.Remove(s3.FirstOrDefault());
context.SaveChanges();
*/
/*
SELECT TOP (1)
[Extent1].[ID] AS [ID],
[Extent1].[Name] AS [Name],
[Extent1].[Class] AS [Class]
FROM [dbo].[Student] AS [Extent1]
WHERE [Extent1].[ID] = 1
DELETE [dbo].[Student] WHERE ([ID] = 1)
*/

// 改
int id = 2;
var s3 = from s in context.Student
where s.ID == id
select s;
var m = s3.FirstOrDefault();
m.Name = "王五";
context.SaveChanges();
/*
SELECT TOP (1)
[Extent1].[ID] AS [ID],
[Extent1].[Name] AS [Name],
[Extent1].[Class] AS [Class]
FROM [dbo].[Student] AS [Extent1]
WHERE [Extent1].[ID] = 2
UPDATE [dbo].[Student] SET [Name] = '王五' WHERE ([ID] = 2)
*/
// 查
// 1. 两者等同
var s1 = context.Student.Select(s => s);
foreach (var item in s1)
{
Console.WriteLine(item.ID);
}
/* 跟踪数据库操作为：
SELECT
[Extent1].[ID] AS [ID],
[Extent1].[Name] AS [Name],
[Extent1].[Class] AS [Class]
FROM [dbo].[Student] AS [Extent1]
*/
var s2 = from s in context.Student
where s.ID > 1 && s.Name.StartsWith("李")
select s.Name;
//
s2 = context.Student.Select(s => s.Name);
foreach (var item in s2)
{
Console.WriteLine(item);
}
/* 跟踪数据库操作为：
SELECT
[Extent1].[Name] AS [Name]
FROM [dbo].[Student] AS [Extent1]
WHERE ([Extent1].[ID] > 1) AND ([Extent1].[Name] LIKE '李%')
*/
}
}
}