该对象无法被删除，因为它在ObjectStateManager中找不到 [英] The object cannot be deleted because it was not found in the ObjectStateManager

问题描述

我有这样的东西：

public void Delete(T entity)
        {
            Context.DeleteObject(entity);
            Context.SaveChanges();
        }

我最终有一个异常：
该对象无法被删除，因为它在ObjectStateManager中找不到。
如果我尝试通过AttachTo（）将实体添加到 objectContext中，我得到：

I end up wit a exception: "The object cannot be deleted because it was not found in the ObjectStateManager." If I try to add the entity to objectContext with AttachTo() I get:

具有相同密钥的对象已经存在于ObjectStateManager中，ObjectStateManager无法跟踪具有相同键的多个对象。

"An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key."

有什么问题？

示例：

namespace CAFM.Data.Repository
{
    public abstract class RepositoryBase<T> : IRepository<T>
        where T : EntityObject
    {
        public RepositoryBase()
            : this(new CAFMRepositoryContext())
        {
        }
        static RepositoryBase()
        {
        }
        public RepositoryBase(IRepositoryContext repositoryContext)
        {
            _context = repositoryContext ?? new CAFMRepositoryContext();
            _entity = _repositoryContext.ObjectContext.CreateObjectSet<T>();
        }
        private readonly ObjectContext _context;
        private readonly ObjectSet<T> _entity;
        protected ObjectContext Context
        {
            get { return _context; }
        }
        protected IObjectSet<T> Entity
        {
            get { return _entity; }
        }



        #region IRepository Members

        private string GetEntityName()
        {
            return string.Format("{0}.{1}", _entity.EntitySet.EntityContainer, _entity.EntitySet.Name);
        }
        public T Add(T entity)
        {
            var fqen = GetEntityName();
            Context.AddObject(fqen, entity);
            Context.SaveChanges(SaveOptions.AcceptAllChangesAfterSave);
            return entity;
        }
        public T Update(T entity)
        {
            Context.ApplyCurrentValues(GetEntityName(), entity);
            Context.SaveChanges(SaveOptions.AcceptAllChangesAfterSave);
            return entity;
        }
        public void Delete(T entity)
        {
            Context.DeleteObject(entity);
            Context.SaveChanges();
        }
        #endregion
    }
}

推荐答案

您必须首先从您的上下文中获取要删除的实体。最好用主键进行比较。它可能看起来像这样，但我不知道 TabMaster 和 TabMasterViewModel 的对象结构，所以属性可能是错误的命名。

You have to fetch the entity you wish to delete from your context first. Best to do this with a comparison of the primary key. It could look like this, but i do not know the object structure of TabMaster and TabMasterViewModel, so the properties may be wrong named.

public void Delete(TabMasterViewModel entity) { 
    TabMaster des = _tabmasterRepository.FirstOrDefault( e.Id = entity.ID );
    if (des != null) {
        _tabmasterRepository.Delete(des); 
    }
} 

您已经创建了一个新的实体，并映射了您对该实体的视图模型。但是上下文不知道实体，所以他不能删除它。

You have created a new Entity and mapped the values from your view model to that entity. But the context does not know of the entity, so he could not delete it.

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