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:ProgramMSSQLServerDBMyFirstEF.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:ProgramMSSQLServerDBMyFirstEF_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

//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

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();
        }
    }
}

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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