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

  public virtual int Remove<T>(List<T> entities) where T : class
        {
            //对象状态管理器设置【删除】状态           
            foreach (var obj in entities)
            {
                _dbContext.Entry(obj).State = EntityState.Deleted;
            }

            //删除
            _dbContext.Set<T>().RemoveRange(entities);

            return SaveChanges(false);
        }