ASP.NET MVC EF直接更新数据(不需查询)

EF(EntityFrameWork) ORM(对象关系映射框架/数据持久化框架)，根据实体对象操作数据表中数据的一种面向对象的操作框架，底层也是调用ADO.NET

ASP.NET MVC 项目会自动导入MVC程序集，因为默认.NET环境(GAC)中没有这个程序集

1: EF数据上下文继承于 DbContext ; DBQuery<T> ，支持延迟加载：只有当使用到数据的时候，才去查询数据库; 主要成员：表映射的实体集合 Set<T>,Entry<T>()

　　context.Model -->Dbset<Model>

　　context.set<Model>() -->Dbset<Model>

　　//使用状态版的时候，执行修改/删除的时候必须指定主键。

2: EF中会为每个管理的实体对象创建一个代理包装类对象，其中会跟踪实体对象的状态和每个属性的状态;

3: [EF对象管理容器]: 每个通过EF数据上下文操作的实体对象，都需要存在上下文的容器中，一旦通过上下文的某个方法操作了实体对象后，那么上下文就会给它加一个状态标识。

但调用上下文的SaveChanges方法的时候，上下文就会遍历容器中的所有对象，并检查他们的状态标识，并依照标识的值进行相应的增删改查sql操作

一、通常使用EF更新的方式，先查询出要修改的数据，然后再修改新的值；实体对象被修改的属性在代理包装类对象里的对应属性状态会被修改记录下修改状态，

等到调用SaveChanges时，EF会遍历其管理的每个实体对象，并根据其包装类对象的状态，生成增删改查sql语句并执行；

此例中修改操作，会生成修改的sql语句（注意：此处只为修改过的属性生成sql语句），最后执行。

 1 create database MyFirstEF
 2 on primary
 3 (
 4     name='MyFirstEF.mdf',
 5     --修改为自己电脑上SQL DB路径
 6     filename='E:\ProgramMSSQLServerDB\MyFirstEF.mdf',
 7     size=5mb,
 8     maxsize=100mb,
 9     filegrowth=10%
10 )
11 log on
12 (
13     name='MyFirstEF_log.ldf',
14     --修改为自己电脑上SQL DB路径
15     filename='E:\ProgramMSSQLServerDB\MyFirstEF_log.ldf',
16     size=2mb,
17     maxsize=100mb,
18     filegrowth=5mb
19 )
20 go
21 
22 use MyFirstEF
23 go
24 
25 create table CustomerInfo
26 (
27     id int identity(1,1) primary key,
28     customerName nvarchar(100) not null,
29     customerDate datetime
30 )
31 go
32 
33 insert into CustomerInfo values('aaaaa',getdate())
34 go
35 
36 select * from CustomerInfo
37 go
38 
39 create table OrderInfo
40 (
41   id int identity(1,1) primary key,
42   orderName nvarchar(100),
43   customerId int
44 )
45 go
46 
47 
48 alter table OrderInfo
49 add constraint FK_OrderInfo_CustomerInfo
50 foreign key(customerId) references CustomerInfo(id)
51 on delete cascade
52 on update cascade
53 
54 go
55 
56 
57 select * from CustomerInfo
58 select * from OrderInfo

create SQL

//EF context 对象
MyFirstEFEntities context = new MyFirstEFEntities();

//update
//1：先查询要修改的原数据
CustomerInfo customer = context.CustomerInfoes.Find(1);
//2：设置修改后的值
customer.customerDate = DateTime.Now;
//3：更新到数据库
context.SaveChanges();

二、为避免先查询数据库，可以直接将被修改的实体对象添加到 EF中管理(此时为附加状态Attached)，并手动设置其为未修改状态(Unchanged)，

同时设置被修改的实体对象的包装类对象对应属性为修改状态。

//EF context 对象
DbContext contextState = new MyFirstEFEntities();

//update
CustomerInfo customerState = new CustomerInfo();
customerState.id = 1;
customerState.customerDate = DateTime.Now;
customerState.customerName = "bbb";

//1: 标记当前对象，必须把必填字段都填写，否则会报错：System.Data.Entity.Validation.DbEntityValidationException
//1: 若此时未更新 非必填字段，则数据库会把非必填字段更新为null
contextState.Entry<CustomerInfo>(customerState).State = System.Data.EntityState.Modified;
contextState.SaveChanges();

//EF context 对象
DbContext contextState = new MyFirstEFEntities();

//update 2
CustomerInfo customerState = new CustomerInfo();
customerState.id = 1;
customerState.customerName = "dfdfdfdf";

//2: 针对某个属性，进行状态跟踪设置
//** 2.1: 如果使用 Entry 附加 实体对象到数据容器中，则需要手动 设置 实体包装类的对象 的 状态为 Unchanged**
//** 2.1: entry.State = System.Data.EntityState.Unchanged;
DbEntityEntry<CustomerInfo> entry = contextState.Entry<CustomerInfo>(customerState);
entry.State = System.Data.EntityState.Unchanged;
entry.Property("customerName").IsModified = true;
contextState.SaveChanges();

//EF context 对象
DbContext contextState = new MyFirstEFEntities();

//update 3
CustomerInfo customerState = new CustomerInfo();
customerState.id = 1;
customerState.customerName = "aaaaa";

//** 2.2: 如果使用 Attach 就不需要这句
//** 2.2: entry.State = System.Data.EntityState.Unchanged;
contextState.Set<CustomerInfo>().Attach(customerState);///直接针对属性进行状态设置，但是当前对象并没有被上下文跟踪
contextState.Entry<CustomerInfo>(customerState).Property("customerName").IsModified = true;
contextState.SaveChanges();

EF其他操作(多表增加操作/导航属性)：

#region 多表增加操作
DbContext dbContext = new MyFirstEFEntities();

CustomerInfo customerInfo = new CustomerInfo()
{
    customerName = "duobiaocaozuo",
    customerDate = DateTime.Now
};
dbContext.Set<CustomerInfo>().Add(customerInfo);

OrderInfo orderInfo1 = new OrderInfo()
{
    orderName = "bike1",
    customerId = customerInfo.id
};
dbContext.Set<OrderInfo>().Add(orderInfo1);

OrderInfo orderInfo2 = new OrderInfo()
{
    orderName = "bike2",
    customerId = customerInfo.id
};
dbContext.Set<OrderInfo>().Add(orderInfo2);

dbContext.SaveChanges();
#endregion

#region 导航属性
DbContext dbContext = new MyFirstEFEntities();

CustomerInfo customerInfo = new CustomerInfo()
{
    customerName = "daohangshuxing",
    customerDate = DateTime.Now
};

customerInfo.OrderInfoes.Add(new OrderInfo()
{
    orderName = "car1",
});

customerInfo.OrderInfoes.Add(new OrderInfo()
{
    orderName = "car2"
});

dbContext.Set<CustomerInfo>().Add(customerInfo);

dbContext.SaveChanges();

#endregion

  1 using System;
  2 using System.Collections.Generic;
  3 using System.Data.Entity;
  4 using System.Data.Entity.Infrastructure;
  5 using System.Linq;
  6 using System.Text;
  7 using System.Threading.Tasks;
  8 
  9 namespace _20160403_MyFirstEFDemo
 10 {
 11     class Program
 12     {
 13         static void Main(string[] args)
 14         {
 15 
 16             #region 方法
 17             ////EF context 对象
 18             //MyFirstEFEntities context = new MyFirstEFEntities();
 19             ////add
 20             //CustomerInfo customer = new CustomerInfo();
 21             //customer.customerName = "Test1";
 22             //customer.customerDate = DateTime.Now;
 23             //context.CustomerInfoes.Add(customer);
 24             //context.SaveChanges();
 25 
 26             ////update
 27             ////1：先查询要修改的原数据
 28             //CustomerInfo customer = context.CustomerInfoes.Find(1);
 29             ////2：设置修改后的值
 30             //customer.customerDate = DateTime.Now;
 31             ////3：更新到数据库
 32             //context.SaveChanges();
 33 
 34             ////Read
 35             //CustomerInfo customer = context.CustomerInfoes.Find(1);
 36             //if (customer != null)
 37             //{
 38             //    string strCustomerInfo = string.Format("name:{0},date:{1}", customer.customerName, customer.customerDate);
 39             //    Console.WriteLine(strCustomerInfo);
 40             //}
 41 
 42             ////delete
 43             //CustomerInfo customer = new CustomerInfo();
 44             //customer.id = 1;
 45             //context.CustomerInfoes.Attach(customer);
 46             //context.CustomerInfoes.Remove(customer);
 47             //context.SaveChanges();
 48             #endregion
 49 
 50             #region 状态
 51             //EF context 对象
 52             //DbContext contextState = new MyFirstEFEntities();
 53 
 54             ////add 1
 55             //CustomerInfo customerState = new CustomerInfo();
 56             //customerState.customerName = "testState1";
 57             //customerState.customerDate = DateTime.Now;
 58             //contextState.Set<CustomerInfo>().Add(customerState);
 59             //contextState.SaveChanges();
 60 
 61             ////add 2
 62             //CustomerInfo customerState = new CustomerInfo() { 
 63             //     customerName="stateTest111",
 64             //     customerDate=DateTime.Now
 65             //};
 66             //contextState.Entry<CustomerInfo>(customerState).State = System.Data.EntityState.Added;
 67             //contextState.SaveChanges();
 68 
 69             ////update 1
 70             //CustomerInfo customerState = new CustomerInfo();
 71             //customerState.id = 1;
 72             //customerState.customerDate = DateTime.Now;
 73             //customerState.customerName = "bbb";
 74 
 75             ////1: 标记当前对象，必须把必填字段都填写，否则会报错：System.Data.Entity.Validation.DbEntityValidationException
 76             ////1: 若此时未更新 非必填字段，则数据库会把非必填字段更新为null
 77             //contextState.Entry<CustomerInfo>(customerState).State = System.Data.EntityState.Modified;
 78             //contextState.SaveChanges();
 79 
 80             ////update 2
 81             //CustomerInfo customerState = new CustomerInfo();
 82             //customerState.id = 1;
 83             //customerState.customerName = "dfdfdfdf";
 84 
 85             ////2: 针对某个属性，进行状态跟踪设置
 86             ////** 2.1: 如果使用 Entry 附加 实体对象到数据容器中，则需要手动 设置 实体包装类的对象 的 状态为 Unchanged**
 87             ////** 2.1: entry.State = System.Data.EntityState.Unchanged;
 88             //DbEntityEntry<CustomerInfo> entry = contextState.Entry<CustomerInfo>(customerState);
 89             //entry.State = System.Data.EntityState.Unchanged;
 90             //entry.Property("customerName").IsModified = true;
 91             //contextState.SaveChanges();
 92 
 93             ////update 3
 94             //CustomerInfo customerState = new CustomerInfo();
 95             //customerState.id = 1;
 96             //customerState.customerName = "aaaaa";
 97 
 98             ////** 2.2: 如果使用 Attach 就不需要这句
 99             ////** 2.2: entry.State = System.Data.EntityState.Unchanged;
100             //contextState.Set<CustomerInfo>().Attach(customerState);///直接针对属性进行状态设置，但是当前对象并没有被上下文跟踪
101             //contextState.Entry<CustomerInfo>(customerState).Property("customerName").IsModified = true;
102             //contextState.SaveChanges();
103 
104             ////delete
105             //CustomerInfo customerState = new CustomerInfo()
106             //{
107             //    id = 2
108             //};
109             //contextState.Entry<CustomerInfo>(customerState).State = System.Data.EntityState.Deleted;
110             //contextState.SaveChanges();
111 
112             #endregion
113 
114             #region 多表增加操作
115             //DbContext dbContext = new MyFirstEFEntities();
116 
117             //CustomerInfo customerInfo = new CustomerInfo()
118             //{
119             //    customerName = "duobiaocaozuo",
120             //    customerDate = DateTime.Now
121             //};
122             //dbContext.Set<CustomerInfo>().Add(customerInfo);
123 
124             //OrderInfo orderInfo1 = new OrderInfo()
125             //{
126             //    orderName = "bike1",
127             //    customerId = customerInfo.id
128             //};
129             //dbContext.Set<OrderInfo>().Add(orderInfo1);
130 
131             //OrderInfo orderInfo2 = new OrderInfo()
132             //{
133             //    orderName = "bike2",
134             //    customerId = customerInfo.id
135             //};
136             //dbContext.Set<OrderInfo>().Add(orderInfo2);
137 
138             //dbContext.SaveChanges();
139             #endregion
140 
141             #region 导航属性
142             //DbContext dbContext = new MyFirstEFEntities();
143 
144             //CustomerInfo customerInfo = new CustomerInfo()
145             //{
146             //    customerName = "daohangshuxing",
147             //    customerDate = DateTime.Now
148             //};
149 
150             //customerInfo.OrderInfoes.Add(new OrderInfo()
151             //{
152             //    orderName = "car1",
153             //});
154 
155             //customerInfo.OrderInfoes.Add(new OrderInfo()
156             //{
157             //    orderName = "car2"
158             //});
159 
160             //dbContext.Set<CustomerInfo>().Add(customerInfo);
161 
162             //dbContext.SaveChanges();
163 
164             #endregion
165 
166             Console.WriteLine("OK");
167             Console.ReadKey();
168         }
169     }
170 }

EF(方法/状态/多表操作/导航属性)整体测试代码

参考文章：

ASP.NET EF(LINQ/Lambda查询)：http://www.cnblogs.com/Dr-Hao/p/5356928.html

ASP.NET EF 使用LinqPad 快速学习Linq：http://www.cnblogs.com/Dr-Hao/p/5357112.html

Ps:ViewBag,ViewData,TempData区别？

ViewBag 和 ViewData 数据"共享"，作用域为当前 Action。

TempData 作用域跨 Action。

来源：https://www.cnblogs.com/DrHao/p/5255630.html

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