Student studentToDelete; . Get student from DB using (var ctx = new SchoolDBEntities()) { studentToDelete = ctx.Students.Where(s => s.StudentName == "Student1").FirstOrDefault<Student>(); } //Create new context for disconnected scenario…

using System; using System.Collections.Generic; public partial class Student { public Student() { this.Courses = new HashSet<Course>(); } public int StudentID { get; set; } public string StudentName { get; set; } public Nullable<int> StandardI…

using System; using System.Collections.Generic; public partial class Student { public Student() { this.Courses = new HashSet<Course>(); } public int StudentID { get; set; } public string StudentName { get; set; } public Nullable<int> StandardI…

使用主键属性 每个实体必须有主键 默认值的id属性值必须为0 在context2中,它不知道实体的状态, 只能通过实体的主键来判断实体的状态 如果主键为0,则是新的对象,不为0 就是修改 Standard disconnectedStandard = null; using (var context = new SchoolDBEntities()) { context.Configuration.ProxyCreationEnabled = false; disconnectedStandar…

//Create student in disconnected mode Student newStudent = new Student() { StudentName = "New Single Student" }; //Assign new standard to student entity newStudent.Standard = new Standard() { StandardName = "New Standard" }; //add new…

可以为实体实现自定义验证,重写DBContext中的个ValidateEntity方法 protected override System.Data.Entity.Validation.DbEntityValidationResult ValidateEntity(DbEntityEntry entityEntry, System.Collections.Generic.IDictionary<object, object> items) { if (entityEntry.Entity is…

You can change the color of an entity in the designer so that it would be easy to see related groups of entities in the designer from Visual Studio 2012 onwards. To change the color of an entity, select entity in the designer → go to property window…

即使延迟加载不能使用,也可以通过明确的调用来延迟加载相关实体 使用DBEntryEntity来完成 using (var context = new SchoolDBEntities()) { //Disable Lazy loading context.Configuration.LazyLoadingEnabled = false; var student = (from s in context.Students where s.StudentName == "Bill" sel…

Entity Framework DBContext 增删改查深度解析 有一段时间没有更新博客了,赶上今天外面下雨,而且没人约球,打算把最近对Entity Framework DBContext使用的心得梳理一下,早些时候在网上简单查过,对于最新版本的EF并没有类似的知识梳理类文章,希望对大家有所帮助. 1. 不要Code first, 也不要DB first 我为什么讨厌Code first和DB first呢?首先Code first是先写代码,数据库完全由代码生成,开发阶段尚可,一旦到了产…

DbContextScope A simple and flexible way to manage your Entity Framework DbContext instances. DbContextScope was created out of the need for a better way to manage DbContext instances in Entity Framework-based applications. The commonly advocated met…