实体框架延迟加载的专用后备字段 [英] Private backing field for entity framework lazy loading

问题描述

我正在使用启用了延迟加载的Entity Framework 5.我有以下代码:

I'm using Entity Framework 5 with lazy loading enabled. I have got the following code:

    private ICollection<Subscription> _subscriptions = new Collection<Subscription>();

    public virtual ICollection<Subscription> Subscriptions
    {
        get { return _subscriptions; }
        set { _subscriptions = value; }
    }

但这有意义吗?我想确保公共属性Subscriptions永远不会为空.由于虚拟实体框架覆盖了getter和setter以提供延迟加载功能.

But does this make sense? I want to ensure that the public property Subscriptions is never null. Due to the virtual entity framework overrides the getter and setter to provide the lazy loading functionality.

我是否需要此字段，或者是否可以仅使用auto属性，如果没有订阅，我会得到一个空列表?

Do I need this field or can I just use an auto property and I get an empty list if there is no Subscription?

推荐答案

如果对象是通过 new 关键字构造的，则您的代码将起作用.但是请注意，许多序列化程序会导致对象构造函数和字段初始化程序不起作用.

Your code will work if the object is constructed via the new keyword. Note however that many serializers function such that object constructors and field initializers do not work.

由于这个原因，我选择了以下模式:

I have settled on the following pattern for that reason:

private ICollection<Subscription> _subscriptions;

public virtual ICollection<Subscription> Subscriptions
{
    get 
    {   
        if (_subscriptions == null) _subscriptions = 
            new Collection<Subscription>();

        return _subscriptions; 
    }
    set { _subscriptions = value; }
}

此代码模式适用于EF，无论对象是使用 new 实例化还是使用不运行对象初始化代码的序列化程序实例化.

This code pattern works with EF, and works whether the object is instantiated with new or with a serializer that doesn't run the object's initialization code.

get 也可以使用null运算符更紧凑地编写:

The get can also be more compactly written using the null-coalescing operator:

    get 
    {   
        return _subscriptions ?? (_subscriptions = 
            new Collection<Subscription>()); 
    }

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