通用实体框架存储库的更新方法 [英] Update method for generic Entity framework repository

问题描述

我有一个这样的存储库：

I have a repository like that:

public class Repository<T> : IRepository<T> where T : class 
{
    private readonly IRepositoryContext _repositoryContext;

    public Repository(IRepositoryContext repositoryContext)
    {
        _repositoryContext = repositoryContext;
        _objectSet = repositoryContext.GetObjectSet<T>();
    }

    public virtual void Update(T entity)
    {
        ObjectSet.AddObject(entity);
        _repositoryContext.ObjectContext.ObjectStateManager.ChangeObjectState(entity, EntityState.Modified);
        _repositoryContext.SaveChanges();
    }
  }

现在实际上适用于实体的所有标量属性，但是与实体 typeOf（T）的属性相关联的所有其他实体不关心实体状态被修改，EF简单地添加新数据。

Now that actually works for all scalar properties of the entity, but all the other entities that associated with properties of entity typeOf(T), don't care that entity state is modified, and EF simply adds new data.

所以，如果你做例如 Repository< Student> .Update（），你只更改了名字，它会找到正确的学生，并更改他的名字，但它也会改变校园，虽然你已经有一个校园与该学生相关联，它将再次创建与不同的校园标识。

So, if you do for example Repository<Student>.Update(), and you only changed the name, it will find the right Student and change his name, but it also will change the Campus, although you already have a Campus associated with that student, it will be created again with a different CampusId.

请在这种情况下向我显示正确的更新方式。

Show me please the correct way to do updates in this situation.

推荐答案

遵循通用方法已被转换为您的代码，例如：

What I did when I wanted to follow generic approach was translated to your code something like:

public class Repository<T> : IRepository<T> where T : class 
{
    ...

    public virtual void Update(T entity)
    {
        if (context.ObjectStateManager.GetObjectStateEntry(entity).State == EntityState.Detached)
        {
            throw new InvalidOperationException(...);
        }

        _repositoryContext.SaveChanges();
    }
}

我的所有代码的工作原理如下：

All my code then worked like:

var attachedEntity = repository.Find(someId);
// Merge all changes into attached entity here
repository.Update(attachedEntity);

=>以通用方式执行此操作会将大量逻辑移动到上层。没有更好的方法来保存大的分离对象图（特别是涉及多对多关系并涉及关系的删除）。

=> Doing this in generic way moves a lot of logic into your upper layer. There is no better way how to save big detached object graphs (especially when many-to-many relations are involved and deleting of relations is involved).

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