无法将类型为"DBContext.Models.Contact"的对象转换为类型为"System.Data.Entity.Infrastructure.IObjectContextAdapter"的对象 [英] Unable to cast object of type 'DBContext.Models.Contact' to type 'System.Data.Entity.Infrastructure.IObjectContextAdapter'

问题描述

我正在尝试实现Contact-Controller中的"Repository-Pattern"，而"Edit"方法正在使用Contact-Repository中的"Attach Method"会引发错误.

I am trying to implement "Repository-Pattern" and "Edit" method in Contact-Controller is making use of "Attach Method" in Contact-Repository is throwing Error.

Additional information: Unable to cast object of type 'Contacts.Models.Contact' to type 'System.Data.Entity.Infrastructure.IObjectContextAdapter'.

在此问题之前，我遇到另一个在代码中找不到ObjectStateManger扩展错误的问题:

Before This issue i faced another issue of ObjectStateManger Extension not found error in the code :

entities.ObjectStateManager.ChangeObjectState(entity, EntityState.Modified);

因此，我不得不使用新的变量"manager"作为来自另一个线程流堆栈的问题的解决方案(

So i had to use new variable "manager" as a solution for the issue from another stack over flow thread (ObjectStateManager no definition issue) Attach Method in Contact-Repository

public void Attach(Contact entity)
        {
            if (entity == null)
                throw new ArgumentNullException("entity");

           var manager = ((IObjectContextAdapter)entity).ObjectContext.ObjectStateManager;

            entities.Contacts.Attach(entity);

           manager.ChangeObjectState(entity, EntityState.Modified);

        }

使用ControllerRespository的Contact Controller中的

Edit方法

Edit Method in Contact Controller that makes use of ContactRespository

public ActionResult Edit(int?id)
            {
                Contact contact = repo.Get(c => c.ID == id);
                if (contact == null)
                {
                    return HttpNotFound();
                }
                return View(contact);
            }


            //
            // POST: /Contacts/Edit/5

            [HttpPost]
            public ActionResult Edit(Contact contact)
            {
                if (ModelState.IsValid)
                {
                    repo.Attach(contact);
                    repo.SaveChanges();
                    return RedirectToAction("Index");
                }
                return View(contact);
            }

推荐答案

在之所以可行，是因为该问题中的OP具有实现IObjectContextAdapter的类型.该问题中的OP具有以下内容:

That works because the OP in that question has a type which implements the IObjectContextAdapter. The OP in that question has this:

SampleContext db = new SampleContext();

您正在尝试这样做:

var manager = ((IObjectContextAdapter)entity).ObjectContext.ObjectStateManager;

您的entity没有实现该接口，因此您不能将其强制转换为IObjectContextAdapter，而这正是错误消息告诉您的内容.

Your entity does not implement that interface so you cannot cast it to IObjectContextAdapter and that is exactly what the error message is telling you.

这篇关于无法将类型为"DBContext.Models.Contact"的对象转换为类型为"System.Data.Entity.Infrastructure.IObjectContextAdapter"的对象的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！