为什么查找一成不变的在C＃中？ [英] Why is Lookup immutable in C#?

问题描述

与词典，你不能用一个元素添加一个构建一个查找。你碰巧知道原因吗？

Unlike Dictionary, you cannot construct a Lookup by adding elements one by one. Do you happen to know the reason?

查找就像多重映射在C ++中;我们为什么不能修改它在C＃中？如果我们真的不能，怎样才能构建在C＃多重映射数据结构？

Lookup is just like multimap in C++; why can't we modify it in C#? If we really can't, how can we construct a multimap data structure in C#?

推荐答案

查找和 ILookup 分别介绍LINQ，通常需要比功能更强大的方法的一部分该框架的其他方面。我个人如的事实，即查找是（至少在公开场合）不变的 - 我期待的more不可改变的集合是可用的。

Lookup and ILookup were introduced as part of LINQ, which generally takes a more functional approach than other aspects of the framework. Personally I like the fact that Lookup is (at least publicly) immutable - and I'm looking forward to more immutable collections being available.

如果你想创建自己的multimap中的数据结构，只是保持一个词典< TKEY的，列表与LT; TValue>> 什么类似。你可能想看看我的 Edulinq实施的查找 一些示例代码。

If you want to create your own multimap data structure, just maintain a Dictionary<TKey, List<TValue>> or something similar. You might want to look at my Edulinq implementation of Lookup for some sample code.

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