具有 Entity Framework 和更新记录的 MVC 存储库模式

Question

我正在尝试在 MVC 应用程序中使用带有 EntityFramework 的存储库模式来更新记录，但是 db.SaveChanges() 方法没有保存到数据库中。我没有收到任何错误，我可以单步执行代码并查看传递的正确变量以及更新的记录变量。

根据我一直在阅读的内容，我相信我的问题是我有两个数据库上下文实例 (MyDBEntities)。问题可能是创建 MyDBEntities 实例的我的 ReadRepository 被注入到 WriteRepository 中，WriteRepository 也创建了一个 MyDBEntities 实例。我不太确定如何将实体注入存储库（假设这是我需要做的）。

如果我尝试在 db.SaveChanges() 之前添加类似 db.MyTable.Attach(record); 的内容，我会在下面收到此错误，这让我觉得我需要注入 MyDBEntities().

An entity object cannot be referenced by multiple instances of IEntityChangeTracker.

控制器

public class MyController : Controller
{
    private IWriteRepository _writeRepository;

    public MyController(IWriteRepository writeRepository)
    {
        _writeRepository = writeRepository;
    }

    [HttpPost]
    public ActionResult MyPostMethod(MyViewModel model)
    {
        try
        {
            //Send to the repository to edit a record
            writeRepository.EditRecord(model);

            return new HttpStatusCodeResult(HttpStatusCode.OK);
        }
        catch
        {
            throw new HttpException(500, "Internal Server Error");
        }            
    }
}

写入存储库

//The ReadRepository is injected into the WriteRepository to grab records from the database
public class WriteRepository : IWriteRepository
{
    private MyDBEntities db = new MyDBEntities();
    private IReadRepository _readRepository;

    public WriteRepository(IReadRepository readeadRepository)
    {
        _readRepository = readRepository;
    }        

    public void EditRecord(MyViewModel model)
    {
        //Get the specific record to be updated
        var record = readRepository.GetRecord(model.ID);

        //Update the data
        record.FirstName = model.Name;

        //This isn't saving
        db.SaveChanges();
    }
}

阅读存储库

public class ReadRepository : IReadRepository
{
    private MyDBEntities db = new MyDBEntities();

    //Provides the record to the write repository to edit
    public MyTable GetRecord(int ID)
    {
        var record = (from t in db.MyTable
                      where t.ID == ID
                      select t).SingleOrDefault();

        return record;
    }
}

Answer 1

从您的 MyController 代码看来您已经在使用控制反转框架，因此请更新您的 ReadRepository 和 WriteRepository class如下：

ReadRepository

public class ReadRepository : IReadRepository
{
    private MyDBEntities db;

    public ReadRepository(MyDBEntities myDbEntities) 
    {
        db = myDbEntities;
    }

    //Provides the record to the write repository to edit
    public MyTable GetRecord(int ID)
    {
        var record = (from t in db.MyTable
                      where t.ID == ID
                      select t).SingleOrDefault();

        return record;
    }
}

WriteRepository

public class WriteRepository : IWriteRepository
{
    private MyDBEntities db;
    private IReadRepository _readRepository;

    public WriteRepository(MyDBEntities myDbEntities, IReadRepository readeadRepository)
    {
        db = myDbEntities;
        _readRepository = readRepository;
    }        

    public void EditRecord(MyViewModel model)
    {
        //Get the specific record to be updated
        var record = readRepository.GetRecord(model.ID);

        //Update the data
        record.FirstName = model.Name;

        //This isn't saving
        db.SaveChanges();
    }
}

你的 ReadRepository 和 WriteRepository 都依赖于 MyDBEntities 的一个实例来工作，因此，您应该在那些 classes 的构造函数中指定该依赖项，并让您的控制反转框架处理创建它，而不是自己创建 MyDBEntities 的新实例。

确保在您的控制反转框架的注册中，您将 MyDBEntities 实例注册为作用域或每个请求，而不是瞬态的。您要确保在每个请求中，您的 ReadRepository 和 WriteRepository 都注入了 MyDBEntities[= 的相同实例50=] class 而不是像现在这样两个单独的实例。

按如下方式更新您的 Unity 配置：

UnityConfig.cs

在每个请求范围内向 Unity 注册您的 MyDBEntities class。

public class UnityConfig { // ... other methods ... public static void RegisterTypes(IUnityContainer container) { // ... other registrations ... container.RegisterType<IReadRepository, ReadRepository>(); container.RegisterType<IWriteRepository, WriteRepository>(); container.RegisterType<MyDBEntities>(new PerRequestLifetimeManager()); // ... other registrations ... } }

UnityMvcActivator.cs

通过取消注释 TODO 下的行，在 Unity 中启用每个请求范围。

public static class UnityWebActivator { public static void Start() { // ... start code ... // TODO: Uncomment if you want to use PerRequestLifetimeManager Microsoft.Web.Infrastructure.DynamicModuleHelper.DynamicModuleUtility.RegisterModule(typeof(UnityPerRequestHttpModule)); } // ... other methods ... }

具有 Entity Framework 和更新记录的 MVC 存储库模式

MVC Repository Pattern with Entity Framework and Updating a Record

asp.net-mvc

entity-framework

dependency-injection

repository-pattern