实体的状态,连接以及 SaveChanges 方法 数据库上下文对象维护内存中的对象与数据库中数据行之间的同步.这些信息在调用 SaveChanges方法被调用的时候使用.例如,当使用 Add 方法传递一个新的实体对象时,实体的状态被设置为 Added,在调用 SaveChanges方法的时候,数据库上下文使用 SQL 命令 Insert来插入数据. 实体的状态可能为如下之一: Added. 实体在数据库中不存在.SaveChanges 方法必须执行 Insert 命令 Unchanged. 在…

Added. The entity does not yet exist in the database. The SaveChanges method must issue an INSERT statement.Unchanged. Nothing needs to be done with this entity by the SaveChanges method. When you read an entity from the database, the entity starts o…

Before we work on CRUD operation (Create, Read, Update, Delete), it's important to understand the entity lifecycle and how it is being managed by the EntityFramework. During an entity's lifetime, each entity has an entity state based on the operation…

在这章中,我们将学习如何创建一个管理图片的新实体,如何使用HTML表单上传图片文件,并使用多对多关系将它们和产品关联起来,如何将图片存储在文件系统中.在这章中,我们还会学习更加复杂的异常处理,如何向模型添加自定义错误,然后向用户显示错误信息.在本章使用的产品图片可以在Apress站点中的第6章的代码中获得. 注意:如果你想按照本章的代码编写示例,你必须完成第五章或者直接从www.apress.com下载第五章的源代码. 6.1 创建一个用于存储图片名称的实体 对于本项目,我们打算使用文件系统将图…

In this post we will be discussing about change tracking feature of Entity Framework Code First. Change tracking allows Entity framework to keep track of all the changes in entities' data. It might involve adding new entities to entities collection o…

Entity Lifecycle: Before we work on CRUD operation (Create, Read, Update, Delete), it's important to understand the entity lifecycle and how it is being managed by the EntityFramework. During an entity's lifetime, each entity has an entity state base…

DBContext: As you have seen in the previous Create Entity Data Model section, EDM generates the SchoolDBEntities class, which was derived from the System.Data.Entity.DbContext class, as shown below. The class that derives DbContext is called context…

DBContext: As you have seen in the previous Create Entity Data Model section, EDM generates the SchoolDBEntities class, which was derived from theSystem.Data.Entity.DbContext class, as shown below. The class that derives DbContext is called context c…

在使用 EF Code First 的时候,我们经常会对项目中的 Entry 进行一对多.多对多的映射配置,这时候就会产生主实体和子实体的概念,我们在添加.修改他们的时候,有时候会产生一些问题,比如添加主实体的时候,我们不想添加子实体,看一个 User-Role 场景: public class User { public int Id { get; set; } public string Name { get; set; } public string Age { get; set; } p…

英文渣水平,大伙凑合着看吧…… 这是微软官方SignalR 2.0教程Getting Started with Entity Framework 6 Code First using MVC 5 系列的翻译,这里是第二篇:实现基本的CRUD功能 原文:Implementing Basic CRUD Functionality with the Entity Framework in ASP.NET MVC Application 译文版权所有,谢绝全文转载——但你可以在你的网站上添加到该教程的链…