关于EF 多对多关系，更改已有实体间关系的问题

悬赏园豆：100 [已关闭问题] 关闭于 2012-06-07 11:35

我有如下两个实体类，多对多关系

public class Task : Entity
{      

        public virtual ICollection<Person> Assignees { get; set; }

       
}

    public class Person : Entity
    {
      
        public virtual ICollection<Task> AcceptedTasks { get; set; }

    }

以下的mapping代码

            HasMany(t => t.Assignees).WithMany(p => p.AcceptedTasks).Map(m =>
            {
                m.MapLeftKey("TaskId").MapRightKey("PersonId").ToTable("Person_AcceptedTask");
            });

一下是出问题的方法：

 public void DesignateTask(Domain.Model.Task task, IEnumerable<Domain.Model.Person> persons, Domain.Model.Person charge = null)
        {
            try
            {
                if (charge == null || charge.IsTransient())
                {
                    charge = persons.FirstOrDefault();
                }

                if (!charge.IsTransient())
                {
                    if (task.Assignees == null)
                        task = TaskRepository.GetTaskWithAssignees(task.Id);

                    TaskRepository.TrackItem(task);//call:Entry<TEntity>(item).State = System.Data.EntityState.Unchanged;
                    task.InChargeId = charge.Id;
                    foreach (var p in persons)
                    {
                        if (p != null)
                            task.Assignees.Add(p);
                    }

                    TaskRepository.UnitOfWork.Commit();//call:SaveChanges();
                }

            }
            catch (Exception)
            {
                TaskRepository.UnitOfWork.Rollback();
                throw;
            }
        }