我怎样才能使一个只读的ObservableCollection的财产？ [英] How can I make a read-only ObservableCollection property?

问题描述

我想公开在包含对象的列表（从数据库）视图模型的属性。

I'd like to expose a property on a view model that contains a list of objects (from database).

我需要为只读此集合。也就是说，我想prevent添加/删除等，但允许在foreach和索引工作。我的目的是定义一个私有字段拿着编辑收集和只读公共属性引用它。如下：

I need this collection to be read-only. That is, I want to prevent Add/Remove, etc. But allow the foreach and indexers to work. My intent is to declare a private field holding the editable collection and reference it with a read-only Public Property. As follows

public ObservableCollection<foo> CollectionOfFoo { 
     get { 
         return _CollectionOfFoo;
     }
}

不过，这种语法只是prevents改变引用集合。它并不prevent添加/删除等。

However, that syntax just prevents changing the reference to the collection. It doesn't prevent add/remove, etc.

什么是正确的方式做到这一点？

What is the right way to accomplish this?

推荐答案

在 [previously] 的接受的答案实际上将返回一个不同的 ReadOnlyObservableCollection每次ReadOnlyFoo是访问。这是浪费的，并可能导致微妙的错误。

The [previously] accepted answer will actually return a different ReadOnlyObservableCollection every time ReadOnlyFoo is accessed. This is wasteful and can lead to subtle bugs.

一个preferable的解决方案是：

A preferable solution is:

public class Source
{
    Source()
    {
        m_collection = new ObservableCollection<int>();
        m_collectionReadOnly = new ReadOnlyObservableCollection<int>(m_collection);
    }

    public ReadOnlyObservableCollection<int> Items
    {
        get { return m_collectionReadOnly; }
    }

    readonly ObservableCollection<int> m_collection;
    readonly ReadOnlyObservableCollection<int> m_collectionReadOnly;
}

请参阅<一href="http://$c$c.logos.com/blog/2009/03/readonlyobservablecollection_anti-pattern.html">ReadOnlyObservableCollection反模式获取充分的讨论。

See ReadOnlyObservableCollection anti-pattern for a full discussion.

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