ASP.NET MVC EF直接更新數據(不需查詢)

EF(EntityFrameWork) ORM(對象關系映射框架/數據持久化框架)，根據實體對象操作數據表中數據的一種面向對象的操作框架，底層也是調用ADO.NET

ASP.NET MVC 項目會自動導入MVC程序集，因為默認.NET環境(GAC)中沒有這個程序集

 1: EF數據上下文 繼承於 DbContext ; DBQuery<T> ，支持延遲加載：只有當使用到數據的時候，才去查詢數據庫; 主要成員：表映射的實體集合 Set<T>,Entry<T>()

　　context.Model -->Dbset<Model>

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

　　//使用狀態版的時候，執行修改/刪除的時候必須指定主鍵。

 2: EF中會為每個 管理的 實體對象 創建一個代理包裝類對象，其中會跟蹤 實體對象 的狀態和每個屬性的狀態;

 3: [EF對象管理容器]: 每個通過EF數據上下文操作的實體對象，都需要存在上下文的容器中，一旦通過上下文的某個方法操作了實體對象后，那么上下文就會給它加一個狀態標識。

     但調用上下文的SaveChanges方法的時候，上下文就會遍歷容器中的所有對象，並檢查他們的狀態標識，並依照標識的值進行相應的增刪改查sql操作

一、通常使用EF更新的方式，先查詢出要修改的數據，然后再修改新的值；實體對象被修改的屬性 在 代理包裝類對象里 的對應屬性狀態會被修改記錄下修改狀態，

      等到調用SaveChanges時，EF會遍歷其管理的每個實體對象，並根據其 包裝類對象 的狀態，生成增刪改查sql語句並執行；

      此例中修改操作，會生成 修改的sql語句（注意：此處只為修改過的屬性生成sql語句），最后執行。

create database MyFirstEF
on primary
(
    name='MyFirstEF.mdf',
    --修改為自己電腦上SQL DB路徑
    filename='E:\ProgramMSSQLServerDB\MyFirstEF.mdf',
    size=5mb,
    maxsize=100mb,
    filegrowth=10%
)
log on
(
    name='MyFirstEF_log.ldf',
    --修改為自己電腦上SQL DB路徑
    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

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

//update
//1：先查詢要修改的原數據
CustomerInfo customer = context.CustomerInfoes.Find(1);
//2：設置修改后的值
customer.customerDate = DateTime.Now;
//3：更新到數據庫
context.SaveChanges();

二、為避免先查詢數據庫，可以直接將 被修改的實體對象 添加到 EF中管理(此時為附加狀態Attached)，並手動設置其為未修改狀態(Unchanged)，

     同時設置被修改的實體對象的包裝類對象 對應屬性為修改狀態。

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

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

//1: 標記當前對象，必須把必填字段都填寫，否則會報錯：System.Data.Entity.Validation.DbEntityValidationException
//1: 若此時未更新 非必填字段，則數據庫會把非必填字段更新為null
contextState.Entry<CustomerInfo>(customerState).State = System.Data.EntityState.Modified;
contextState.SaveChanges();

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

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

//2: 針對某個屬性，進行狀態跟蹤設置
//** 2.1: 如果使用 Entry 附加 實體對象到數據容器中，則需要手動 設置 實體包裝類的對象 的 狀態為 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 對象
DbContext contextState = new MyFirstEFEntities();

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

//** 2.2: 如果使用 Attach 就不需要這句
//** 2.2: entry.State = System.Data.EntityState.Unchanged;
contextState.Set<CustomerInfo>().Attach(customerState);///直接針對屬性進行狀態設置，但是當前對象並沒有被上下文跟蹤
contextState.Entry<CustomerInfo>(customerState).Property("customerName").IsModified = true;
contextState.SaveChanges();

EF其他操作(多表增加操作/導航屬性)：

#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 導航屬性
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 對象
            //MyFirstEFEntities context = new MyFirstEFEntities();
            ////add
            //CustomerInfo customer = new CustomerInfo();
            //customer.customerName = "Test1";
            //customer.customerDate = DateTime.Now;
            //context.CustomerInfoes.Add(customer);
            //context.SaveChanges();

            ////update
            ////1：先查詢要修改的原數據
            //CustomerInfo customer = context.CustomerInfoes.Find(1);
            ////2：設置修改后的值
            //customer.customerDate = DateTime.Now;
            ////3：更新到數據庫
            //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 狀態
            //EF context 對象
            //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: 標記當前對象，必須把必填字段都填寫，否則會報錯：System.Data.Entity.Validation.DbEntityValidationException
            ////1: 若此時未更新 非必填字段，則數據庫會把非必填字段更新為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: 針對某個屬性，進行狀態跟蹤設置
            ////** 2.1: 如果使用 Entry 附加 實體對象到數據容器中，則需要手動 設置 實體包裝類的對象 的 狀態為 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 就不需要這句
            ////** 2.2: entry.State = System.Data.EntityState.Unchanged;
            //contextState.Set<CustomerInfo>().Attach(customerState);///直接針對屬性進行狀態設置，但是當前對象並沒有被上下文跟蹤
            //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 導航屬性
            //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();
        }
    }
}

參考文章：

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

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

Ps:ViewBag,ViewData,TempData區別？

ViewBag 和 ViewData 數據"共享"，作用域為 當前 Action。

TempData 作用域跨 Action。