在 C# 中运行时向类型化对象添加 Expando 属性

发布于 2024-10-20 11:15:25 字数 743 浏览 1 评论 0原文

.net 中是否有任何方法可以在运行时将属性字典绑定到实例，即，就好像基对象类具有如下属性：

public IDictionary Items { get; }

我提出了一个涉及静态字典和扩展方法的解决方案，

void Main()
{
    var x = new object();
    x.Props().y = "hello";
}

static class ExpandoExtension {
    static IDictionary<object, dynamic> props = new Dictionary<object, dynamic>();
    public static dynamic Props(this object key)
    { 
        dynamic o;
        if (!props.TryGetValue(key, out o)){
            o = new ExpandoObject();
            props[key] = o;
        }
        return o;       
    } 
}

但这会停止由于 props 集合持有引用，因此对象不会被 GC 回收。事实上，这对于我的特定用例来说是可以的，因为一旦我完成了我正在使用它们的特定任务，我就可以手动清除这些道具，但我想知道，是否有一些巧妙的方法来绑定这些道具ExpandoObject 到键同时允许垃圾回收？

原文

Is there any way in .net to bind a dictionary of properties to an instance at runtime, i.e., as if the base object class had a property like:

public IDictionary Items { get; }

I have come up with a solution involving a static dictionary and extension method

void Main()
{
    var x = new object();
    x.Props().y = "hello";
}

static class ExpandoExtension {
    static IDictionary<object, dynamic> props = new Dictionary<object, dynamic>();
    public static dynamic Props(this object key)
    { 
        dynamic o;
        if (!props.TryGetValue(key, out o)){
            o = new ExpandoObject();
            props[key] = o;
        }
        return o;       
    } 
}

but this stops the objects from getting GC'd as the the props collection holds a reference. In fact, this is just about ok for my particular use case, as I can clear the props down manually once I've finished with the particular thing I'm using them for, but I wonder, is there some cunning way to tie the ExpandoObject to the key while allowing garbage collection?

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我也只是我 2024-10-27 11:15:25

查看 ConditionalWeakTable类。

ConditionalWeakTable类使语言编译器能够在运行时将任意属性附加到托管对象。 ConditionalWeakTableobject 是一个字典，它将由键表示的托管对象绑定到由值表示的附加属性。对象的键是属性所附加到的 TKey 类的各个实例，其值是分配给相应对象的属性值。

本质上，它是一个字典，其中键和值都是弱引用的，并且只要键还活着，值就保持活动状态。

static class ExpandoExtensions
{
    private static readonly ConditionalWeakTable<object, ExpandoObject> props =
        new ConditionalWeakTable<object, ExpandoObject>();

    public static dynamic Props(this object key)
    { 
        return props.GetOrCreateValue(key);       
    } 
}

Have a look at the ConditionalWeakTable<TKey, TValue> Class.

The ConditionalWeakTable<TKey, TValue> class enables language compilers to attach arbitrary properties to managed objects at run time. A ConditionalWeakTable<TKey, TValue> object is a dictionary that binds a managed object, which is represented by a key, to its attached property, which is represented by a value. The object's keys are the individual instances of the TKey class to which the property is attached, and its values are the property values that are assigned to the corresponding objects.

Essentially it's a dictionary where both the keys and the values are weakly referenced, and a value is kept alive as long as the key is alive.

static class ExpandoExtensions
{
    private static readonly ConditionalWeakTable<object, ExpandoObject> props =
        new ConditionalWeakTable<object, ExpandoObject>();

    public static dynamic Props(this object key)
    { 
        return props.GetOrCreateValue(key);       
    } 
}

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