使字典只读在C＃ [英] Make dictionary read only in C#

问题描述

我有一个字典< string，List< string>> ，并希望将成员公开为只读。我看到我可以返回它作为 IReadOnlyDictionary< string，List< string>> ，但我不知道如何返回它作为 IReadOnlyDictionary< string，IReadOnlyList< string>> 。

I have a Dictionary<string, List<string>> and would like to expose the member as read only. I see that I can return it as a IReadOnlyDictionary<string, List<string>>, but I can't figure out how to return it as an IReadOnlyDictionary<string, IReadOnlyList<string>>.

有办法吗？在c ++中我只是使用const，但C＃没有这个。

Is there a way to do this? In c++ I'd just be using const, but C# doesn't have that.

注意，只需使用 IReadOnlyDictionary 在这种情况下没有帮助，因为我想要的值也只读。看来唯一的方法是创建另一个IReadOnlyDictionary，并添加IReadOnlyList给他们。

Note that simply using a IReadOnlyDictionary does not help in this case, because I want the values to be read only as well. It appears the only way to do this is build another IReadOnlyDictionary, and add IReadOnlyList to them.

另一个选项，我不会很兴奋，将创建包装器，它实现了接口IReadOnlyDictionary>，并且它拥有原始实例的副本，但似乎过分。

Another option, which I wouldn't be thrilled with, would be to create wrapper which implements the interface IReadOnlyDictionary>, and have it hold a copy of the original instance, but that seems overkill.

推荐答案

将像将字典引用 IReadOnlyDictionary< string，IReadOnlyList< string>> 一样简单，因为 Dictionary< TKey，TValue> implements IReadOnlyDictionary< TKey，TValue> 。

It would be as easy as casting the whole dictionary reference to IReadOnlyDictionary<string, IReadOnlyList<string>> because Dictionary<TKey, TValue> implements IReadOnlyDictionary<TKey, TValue>.

希望 List< string> 值为 IReadOnlyList< string> 。

所以你需要这样的：

var readOnlyDict = (IReadOnlyDictionary<string, IReadOnlyList<string>>)dict.ToDictionary(pair => pair.Key, pair.Value.AsReadOnly());

不可改写的字典

建议，但如果您要查找不可变的字典，请添加 系统.Collections.Immutable NuGet包到您的解决方案，您就可以使用它们：

Immutable dictionaries

This is just a suggestion, but if you're looking for immutable dictionaries, add System.Collections.Immutable NuGet package to your solution and you'll be able to use them:

// ImmutableDictionary<string, ImmutableList<string>>
var immutableDict = dict.ToImmutableDictionary(pair => pair.Key, pair.Value.ToImmutableList());

进一步了解不可变的集合。

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