标签：from blog mis stat 数据 color text pre creation
EntityFramework默认支持乐观并发
乐观并发中，实体加载后如果都没发生变化，ef保存该实体
首先，我们需要一个rowversion列为了控制student实体的并发问题，rowversion的数据类型为字节数组，rowversion像是自增id，
rowversion的值在数据库当中自动添加和更新
ef将在where子句中添加rowversion列，当你进行更新操作，如果rowversion的值与where子句中的值不一致，则抛出异常
Student student1WithUser1 = null; Student student1WithUser2 = null; //User 1 gets student using (var context = new SchoolDBEntities()) { context.Configuration.ProxyCreationEnabled = false; student1WithUser1 = context.Students.Where(s => s.StudentID == 1).Single(); } //User 2 also get the same student using (var context = new SchoolDBEntities()) { context.Configuration.ProxyCreationEnabled = false; student1WithUser2 = context.Students.Where(s => s.StudentID == 1).Single(); } //User 1 updates Student name student1WithUser1.StudentName = "Edited from user1"; //User 2 updates Student name student1WithUser2.StudentName = "Edited from user2";
//User 1 saves changes first using (var context = new SchoolDBEntities()) { try { context.Entry(student1WithUser1).State = EntityState.Modified; context.SaveChanges(); } catch (DbUpdateConcurrencyException ex) { Console.WriteLine("Optimistic Concurrency exception occured"); } } //User 2 saves changes after User 1. //User 2 will get concurrency exection //because CreateOrModifiedDate is different in the database using (var context = new SchoolDBEntities()) { try { context.Entry(student1WithUser2).State = EntityState.Modified; context.SaveChanges(); } catch (DbUpdateConcurrencyException ex) { Console.WriteLine("Optimistic Concurrency exception occured"); } }
标签：from blog mis stat 数据 color text pre creation
原文地址：http://www.cnblogs.com/lanpingwang/p/6618897.html
