C# ASP.net MVC EF Codefirst重复条目
使用Asp.NETMVC4和EF5.0 问题:C# ASP.net MVC EF Codefirst重复条目,c#,asp.net,entity-framework,ef-code-first,duplicates,C#,Asp.net,Entity Framework,Ef Code First,Duplicates,使用Asp.NETMVC4和EF5.0 问题: public class ViewModel { public IQueryable<DinnerEvent> events { get; set; } public IQueryable<User> users { get; set; } } 每当我在dropdownlist中选择一个用户并将帖子提交给Action时。 发生了两件事: 用户被添加到DinnerEvent,其作用是: 选择的用户是重复的,因
public class ViewModel
{
public IQueryable<DinnerEvent> events { get; set; }
public IQueryable<User> users { get; set; }
}
每当我在dropdownlist中选择一个用户并将帖子提交给Action时。
发生了两件事:
这是设置 我创建了两个实体: 晚餐事件和用户
[HttpPost]
public ActionResult AddAttendantToEvent(int users , int EventID )
{
if (ModelState.IsValid)
{
var user = userRepository.Find(users);
dinnereventRepository.Find(EventID).Attendants.Add(user); //Add the User to the Event.
dinnereventRepository.Save();
return RedirectToAction("Index");
}
else
{
return View();
}
}
DinnerEvent类具有指向参与者(用户)集合的导航属性
视图-迭代所有事件,并添加一个包含每个事件的所有用户的下拉列表。
我做错了什么
请求的存储库代码:
public ViewResult Index()
{
ViewModel viewdata = new ViewModel();
viewdata.events = dinnereventRepository.AllIncluding(m => m.Attendants);
viewdata.users = userRepository.All;
return View(viewdata);
}
缩小到只包含Save()方法
注意,这都是脚手架自动生成的代码
public class DinnerEventRepository : IDinnerEventRepository
{
MadklubContext context = new MadklubContext();
public void Save()
{
context.SaveChanges();
}
}
public class MadklubContext : DbContext
{
public DbSet<Madklub.Models.User> Users { get; set; }
public DbSet<Madklub.Models.MadklubEvent> MadklubEvents { get; set; }
}
public class dinnerenterepository:IDinerEventRepository
{
MadklubContext=new MadklubContext();
公共作废保存()
{
SaveChanges();
}
}
公共类MadklubContext:DbContext
{
公共数据库集用户{get;set;}
公共DbSet MadklubEvents{get;set;}
}
工作单元模式:(顺便说一句,使您的回购/uow IDisposable,以便您可以清理DbContext实例)
用法:
[HttpPost]
public ActionResult AddAttendantToEvent(int users , int EventID )
{
if (ModelState.IsValid)
{
// this should be a using statement once you implement IDisposable
// e.g. using( var uow = new RsvpUnitOfWork() ) { ... }
var uow = new RsvpUnitOfWork();
// you need to validate that user != null
var user = uow.UserRepo.Find(users);
// possible null reference exception if dinner event not found for EventID
uow.DinnerEventRepo.Find(EventID).Attendants.Add(user); //Add the User to the Event.
uow.Save();
return RedirectToAction("Index");
}
else
{
return View();
}
}
您可以发布存储库的代码吗?我已经添加了存储库代码,注意:这都是自动生成的代码。@KristianGrønborgNissen,复制的原因是,您正在添加一个分离的实体(因此EF不知道它存在)我认为Johan是对的,您必须添加一个分离的对象。Find方法是否分离该对象?使用工作单元模式;创建一个类,该类具有每个存储库的实例,并将单个DbContext实例传递给每个存储库,以便它们共享相同的DbContext。这就解决了d问题。非常感谢。所以问题是,存储库没有使用同一个DbContext实例?!是的-您将
UserRepository
的上下文中的User
对象引入到dinneretropository
的上下文中,这使它看起来是新的,因此是一个添加/插入操作。
public class DinnerEventRepository : IDinnerEventRepository
{
MadklubContext context = new MadklubContext();
public void Save()
{
context.SaveChanges();
}
}
public class MadklubContext : DbContext
{
public DbSet<Madklub.Models.User> Users { get; set; }
public DbSet<Madklub.Models.MadklubEvent> MadklubEvents { get; set; }
}
public class DinnerEventRepository : IDinnerEventRepository
{
MadklubContext _context = new MadklubContext();
public void Save()
{
_context.SaveChanges();
}
public DinnerEventRepository( MadklubContext context = null )
{
_context = context ?? new MadklubContext();
}
}
public class UserRepository //: IUserRepository
{
MadklubContext _context = new MadklubContext();
public void Save()
{
_context.SaveChanges();
}
public UserRepository( MadklubContext context = null )
{
_context = context ?? new MadklubContext();
}
}
public class RsvpUnitOfWork // come up with a better name
{
MadklubContext _context = new MadklubContext();
public DinnerEventRepository DinnerEventRepo { get; private set; }
public UserRepository UserRepo { get; private set; }
public RsvpUnitOfWork()
{
DinnerEventRepo = new DinnerEventRepository( _context );
UserRepo = new UserRepository( _context );
}
public void Save()
{
_context.SaveChanges();
}
}
[HttpPost]
public ActionResult AddAttendantToEvent(int users , int EventID )
{
if (ModelState.IsValid)
{
// this should be a using statement once you implement IDisposable
// e.g. using( var uow = new RsvpUnitOfWork() ) { ... }
var uow = new RsvpUnitOfWork();
// you need to validate that user != null
var user = uow.UserRepo.Find(users);
// possible null reference exception if dinner event not found for EventID
uow.DinnerEventRepo.Find(EventID).Attendants.Add(user); //Add the User to the Event.
uow.Save();
return RedirectToAction("Index");
}
else
{
return View();
}
}