使用EF删除会导致错误无法删除对象，因为在ObjectStateManager中找不到该对象

Question

当我尝试通过EF 6删除某个对象时，发生错误无法删除该对象，因为在ObjectStateManager中找不到该对象。

但是你可以在图像中看到，TEntity obj正确地接收了一个对象。

代码

public class RepositoryBase<TEntity, TContext> : IRepositoryBase<TEntity>
        where TEntity : class
        where TContext : IDbContext, new()
    {
        private readonly ContextManager<TContext> _contextManager = ServiceLocator.Current.GetInstance<IContextManager<TContext>>() as ContextManager<TContext>;

        protected IDbSet<TEntity> DbSet;
        protected readonly IDbContext Context;

        public RepositoryBase()
        {
            Context = _contextManager.GetContext();
            DbSet = Context.Set<TEntity>();
        }

        public virtual void Add(TEntity obj)
        {
            DbSet.Add(obj);
        }

        public virtual TEntity GetById(Guid id)
        {
            return DbSet.Find(id);
        }

        public virtual IEnumerable<TEntity> GetAll()
        {
            return DbSet.ToList();
        }

        public virtual IEnumerable<TEntity> GetAllReadOnly()
        {
            return DbSet.AsNoTracking();
        }

        public virtual void Update(TEntity obj)
        {
            var entry = Context.Entry(obj);
            DbSet.Attach(obj);
            entry.State = EntityState.Modified;
        }

        public virtual void Remove(TEntity obj)
        {
            DbSet.Remove(obj);
        }

        public virtual IEnumerable<TEntity> Find(Expression<Func<TEntity, bool>> predicate)
        {
            return DbSet.Where(predicate);
        }

        public void Dispose()
        {
            Context.Dispose();
            GC.SuppressFinalize(this);
        }
    }