The object cannot be deleted because it was not found in the ObjectStateManager

I have something like this:

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

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:

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

Whats wrong?

Example:

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;
        }
      开发者_C百科  public void Delete(T entity)
        {
            Context.DeleteObject(entity);
            Context.SaveChanges();
        }
        #endregion
    }
}

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); 
    }
} 

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.

You could just "Attach" the object to the current context like that:

public void Delete(T entity)
{
    context.AttachTo(entity.EntityKey.EntitySetName, entity);
    Context.DeleteObject(entity);
    Context.SaveChanges();
}