我目前正在使用最新版本的 Entity Framework 开发一个项目，我遇到了一个我似乎无法解决的问题。

当谈到更新现有对象时，我可以很容易地更新对象属性，直到涉及到一个引用另一个类的属性。

在下面的示例中，我有一个名为 Foo 的类，它存储各种属性，其中 2 个是其他类的实例

public class Foo
{
     public int Id {get; set;}
     public string Name {get; set;}
     public SubFoo SubFoo {get; set}
     public AnotherSubFoo AnotherSubFoo {get; set}
}

当我使用下面的 Edit() 方法时，我传入了我希望更新的对象，我可以设法让 Name 正确更新，但是我还没有设法找到一种方法来改变 SubFoo 的属性。例如，如果 SubFoo 类具有 Name 属性，并且该属性已更改并且在我的数据库和 newFoo 之间有所不同，它没有得到更新。

public Foo Edit(Foo newFoo)
{
    var dbFoo = context.Foo
        .Include(x => x.SubFoo)
        .Include(x => x.AnotherSubFoo)
        .Single(c => c.Id == newFoo.Id);

    var entry = context.Entry<Foo>(dbFoo);
    entry.OriginalValues.SetValues(dbFoo);
    entry.CurrentValues.SetValues(newFoo);

    context.SaveChanges();

    return newFoo;
}

如有任何帮助或指点，我们将不胜感激。

更新: 根据 Slauma 的评论，我将方法修改为

public Foo Edit(Foo newFoo)
{
    var dbFoo = context.Foo
        .Include(x => x.SubFoo)
        .Include(x => x.AnotherSubFoo)
        .Single(c => c.Id == newFoo.Id);

    context.Entry(dbFoo).CurrentValues.SetValues(newFoo);
    context.Entry(dbFoo.SubFoo).CurrentValues.SetValues(newFoo.SubFoo);

    context.SaveChanges();

    return newFoo;
}

现在运行时，出现错误:

The entity type Collection`1 is not part of the model for the current context.

为了尝试解决这个问题，我添加了代码以尝试将 newFoo 子类附加到上下文中，但这是通过一个错误提示 ObjectManager 已经有一个实体相同:

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

最佳答案

CurrentValues.SetValues 仅更新标量属性但不更新相关实体，因此您必须对每个相关实体执行相同的操作:

public Foo Edit(Foo newFoo)
{
    var dbFoo = context.Foo
                       .Include(x => x.SubFoo)
                       .Include(x => x.AnotherSubFoo)
                       .Single(c => c.Id == newFoo.Id);

    context.Entry(dbFoo).CurrentValues.SetValues(newFoo);
    context.Entry(dbFoo.SubFoo).CurrentValues.SetValues(newFoo.SubFoo);
    context.Entry(dbFoo.AnotherSubFoo).CurrentValues.SetValues(newFoo.AnotherSubFoo);

    context.SaveChanges();

    return newFoo;
}

如果关系可以完全删除或创建，您还需要明确处理这些情况:

public Foo Edit(Foo newFoo)
{
    var dbFoo = context.Foo
                       .Include(x => x.SubFoo)
                       .Include(x => x.AnotherSubFoo)
                       .Single(c => c.Id == newFoo.Id);

    context.Entry(dbFoo).CurrentValues.SetValues(newFoo);
    if (dbFoo.SubFoo != null)
    {
        if (newFoo.SubFoo != null)
        {
            if (dbFoo.SubFoo.Id == newFoo.SubFoo.Id)
                // no relationship change, only scalar prop.
                context.Entry(dbFoo.SubFoo).CurrentValues.SetValues(newFoo.SubFoo);
            else
            {
                // Relationship change
                // Attach assumes that newFoo.SubFoo is an existing entity
                context.SubFoos.Attach(newFoo.SubFoo);
                dbFoo.SubFoo = newFoo.SubFoo;
            }
        }
        else // relationship has been removed
            dbFoo.SubFoo = null;
    }
    else
    {
        if (newFoo.SubFoo != null) // relationship has been added
        {
            // Attach assumes that newFoo.SubFoo is an existing entity
            context.SubFoos.Attach(newFoo.SubFoo);
            dbFoo.SubFoo = newFoo.SubFoo;
        }
        // else -> old and new SubFoo is null -> nothing to do
    }

    // the same logic for AnotherSubFoo ...

    context.SaveChanges();

    return newFoo;
}

如果关系和标量属性已更改，您最终还需要将附加实体的状态设置为已修改。

编辑

如果 - 根据您的评论 - Foo.SubFoo 实际上是一个集合而不仅仅是一个引用，您将需要这样的东西来更新相关实体:

public Foo Edit(Foo newFoo)
{
    var dbFoo = context.Foo
                       .Include(x => x.SubFoo)
                       .Include(x => x.AnotherSubFoo)
                       .Single(c => c.Id == newFoo.Id);

    // Update foo (works only for scalar properties)
    context.Entry(dbFoo).CurrentValues.SetValues(newFoo);

    // Delete subFoos from database that are not in the newFoo.SubFoo collection
    foreach (var dbSubFoo in dbFoo.SubFoo.ToList())
        if (!newFoo.SubFoo.Any(s => s.Id == dbSubFoo.Id))
            context.SubFoos.Remove(dbSubFoo);

    foreach (var newSubFoo in newFoo.SubFoo)
    {
        var dbSubFoo = dbFoo.SubFoo.SingleOrDefault(s => s.Id == newSubFoo.Id);
        if (dbSubFoo != null)
            // Update subFoos that are in the newFoo.SubFoo collection
            context.Entry(dbSubFoo).CurrentValues.SetValues(newSubFoo);
        else
            // Insert subFoos into the database that are not
            // in the dbFoo.subFoo collection
            dbFoo.SubFoo.Add(newSubFoo);
    }

    // and the same for AnotherSubFoo...

    db.SaveChanges();

    return newFoo;
}

关于c# - Entity Framework ，更新相关对象时出现问题，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/13236116/