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。

 create database MyFirstEF
 on primary
 (
     name='MyFirstEF.mdf',
     --修改为自己电脑上SQL DB路径
     filename='E:\ProgramMSSQLServerDB\MyFirstEF.mdf',
     size=5mb,
     maxsize=100mb,
     filegrowth=10%
 )
 log on
 (
     name='MyFirstEF_log.ldf',
     --修改为自己电脑上SQL DB路径
     filename='E:\ProgramMSSQLServerDB\MyFirstEF_log.ldf',
     size=2mb,
     maxsize=100mb,
     filegrowth=5mb
 )
 go

 use MyFirstEF
 go

 create table CustomerInfo
 (
     id int identity(1,1) primary key,
     customerName nvarchar(100) not null,
     customerDate datetime
 )
 go

 insert into CustomerInfo values('aaaaa',getdate())
 go

 select * from CustomerInfo
 go

 create table OrderInfo
 (
   id int identity(1,1) primary key,
   orderName nvarchar(100),
   customerId int
 )
 go

 alter table OrderInfo
 add constraint FK_OrderInfo_CustomerInfo
 foreign key(customerId) references CustomerInfo(id)
 on delete cascade
 on update cascade

 go

 select * from CustomerInfo
 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();
//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 = ;
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 = ;
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 = ;
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

 using System;
 using System.Collections.Generic;
 using System.Data.Entity;
 using System.Data.Entity.Infrastructure;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;

 namespace _20160403_MyFirstEFDemo
 {
     class Program
     {
         static void Main(string[] args)
         {

             #region 方法
             ////EF context 对象
             //MyFirstEFEntities context = new MyFirstEFEntities();
             ////add
             //CustomerInfo customer = new CustomerInfo();
             //customer.customerName = "Test1";
             //customer.customerDate = DateTime.Now;
             //context.CustomerInfoes.Add(customer);
             //context.SaveChanges();

             ////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();

             ////Read
             //CustomerInfo customer = context.CustomerInfoes.Find(1);
             //if (customer != null)
             //{
             //    string strCustomerInfo = string.Format("name:{0},date:{1}", customer.customerName, customer.customerDate);
             //    Console.WriteLine(strCustomerInfo);
             //}

             ////delete
             //CustomerInfo customer = new CustomerInfo();
             //customer.id = 1;
             //context.CustomerInfoes.Attach(customer);
             //context.CustomerInfoes.Remove(customer);
             //context.SaveChanges();
             #endregion

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

             ////add 1
             //CustomerInfo customerState = new CustomerInfo();
             //customerState.customerName = "testState1";
             //customerState.customerDate = DateTime.Now;
             //contextState.Set<CustomerInfo>().Add(customerState);
             //contextState.SaveChanges();

             ////add 2
             //CustomerInfo customerState = new CustomerInfo() {
             //     customerName="stateTest111",
             //     customerDate=DateTime.Now
             //};
             //contextState.Entry<CustomerInfo>(customerState).State = System.Data.EntityState.Added;
             //contextState.SaveChanges();

             ////update 1
             //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();

             ////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();

             ////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();

             ////delete
             //CustomerInfo customerState = new CustomerInfo()
             //{
             //    id = 2
             //};
             //contextState.Entry<CustomerInfo>(customerState).State = System.Data.EntityState.Deleted;
             //contextState.SaveChanges();

             #endregion

             #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

             Console.WriteLine("OK");
             Console.ReadKey();
         }
     }
 }

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

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