如何在 C# 中使用 LINQ 从字典转换为 SortedDictionary？

How do I convert from a Dictionary to a SortedDictionary using LINQ in C#?

提问by Guy

I have a Dictionary<string, double>and I want to convert it to a SortedDictionary<double, string>. How do I do this using LINQ extension methods in C# 3.0?

我有一个Dictionary<string, double>，我想将它转换为一个SortedDictionary<double, string>. 如何使用 C# 3.0 中的 LINQ 扩展方法执行此操作？

EDIT: Generic angle brackets not in original question when Marc and Jared answered.

编辑：当 Marc 和 Jared 回答时，原始问题中没有通用尖括号。

采纳答案by Marc Gravell

editthis answer was before edit; for an answer to the updated problem, see this reply.

编辑此答案是在编辑之前；有关更新问题的答案，请参阅此回复。

Why use LINQ? There is a constructor for this:

为什么要使用 LINQ？有一个构造函数：

new SortedDictionary<int, string>(existing);

You could adda ToSortedDictionary- but I wouldn't bother...

你可以添加一个ToSortedDictionary- 但我不会打扰......

回答by JaredPar

No LINQ is needed. SortedDictionary has a constructor to do the conversion.

不需要 LINQ。SortedDictionary 有一个构造函数来进行转换。

public SortedDictionary<TKey,TValue> Convert<TKey,TValue>(Dictionary<TKey,TValue> map) {
  return new SortedDictionary<TKey,TValue>(map);
}

回答by Bryan Watts

You don't need LINQ, just some nifty extension methods:

你不需要 LINQ，只需要一些漂亮的扩展方法：

public static IDictionary<TKey, TValue> Sort<TKey, TValue>(this IDictionary<TKey, TValue> dictionary)
{
    if(dictionary == null)
    {
        throw new ArgumentNullException("dictionary");
    }

    return new SortedDictionary<TKey, TValue>(dictionary);
}

public static IDictionary<TKey, TValue> Sort<TKey, TValue>(this IDictionary<TKey, TValue> dictionary, IComparer<TKey> comparer)
{
    if(dictionary == null)
    {
        throw new ArgumentNullException("dictionary");
    }

    if(comparer == null)
    {
        throw new ArgumentNullException("comparer");
    }

    return new SortedDictionary<TKey, TValue>(dictionary, comparer);
}

Example usage:

用法示例：

var dictionary = new Dictionary<int, string>
{
    { 1, "one" },
    { 2, "two" },
    { 0, "zero" }
};

foreach(var pair in dictionary.Sort())
{
    Console.WriteLine("{0}: {1}", pair.Key, pair.Value);
}

// 0: zero
// 1: one
// 2: two

回答by Andrew Hare

It seems as though you are asking for an elegant way to take a Dictionary<TKey,TValue>and turn that into a SortedDictionary<TValue,TKey>(note that the value of the Dictionaryis now the key of the SortedDictionary). I don't see any answer addressing that so here it goes.

似乎您正在寻求一种优雅的方式将 aDictionary<TKey,TValue>转换为 a SortedDictionary<TValue,TKey>（请注意， the 的值Dictionary现在是 the 的键SortedDictionary）。我没有看到任何解决这个问题的答案，所以就这样了。

You could create an extension method that looks like this:

您可以创建一个如下所示的扩展方法：

static class Extensions
{
    public static Dictionary<TValue, TKey> 
         AsInverted<TKey, TValue>(this Dictionary<TKey, TValue> source)
    {
        var inverted = new Dictionary<TValue, TKey>();

        foreach (KeyValuePair<TKey, TValue> key in source)
            inverted.Add(key.Value, key.Key);

        return inverted;
    }
}

And your application code would look like this:

您的应用程序代码如下所示：

using System;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        var dict = new Dictionary<String, Double>();
        dict.Add("four", 4);
        dict.Add("three", 3);
        dict.Add("two", 2);
        dict.Add("five", 5);
        dict.Add("one", 1);

        var sortedDict = new SortedDictionary<Double, String>(dict.AsInverted());
    }
}

回答by Bryan Watts

Inversion using ToDictionary:

反转使用ToDictionary：

public static IDictionary<TValue, TKey> Invert<TKey, TValue>(this IDictionary<TKey, TValue> dictionary)
{
    if(dictionary == null)
    {
        throw new ArgumentNullException("dictionary");
    }

    return dictionary.ToDictionary(pair => pair.Value, pair => pair.Key);
}

Example usage:

用法示例：

var dictionary = new Dictionary<string, int>
{
    { "zero", 0 },
    { "one", 1 },
    { "two", 2 }
};

foreach(var pair in dictionary.Invert())
{
    Console.WriteLine("{0}: {1}", pair.Key, pair.Value);
}

// 0: zero
// 1: one
// 2: two

Example of inverting and sorting (see my other answer for the definition of Sort):

反转和排序的示例（有关 的定义，请参阅我的其他答案Sort）：

var dictionary = new Dictionary<string, int>
{
    { "one", 1 },
    { "two", 2 },
    { "zero", 0 }
};

foreach(var pair in dictionary.Invert().Sort())
{
    Console.WriteLine("{0}: {1}", pair.Key, pair.Value);
}

// 0: zero
// 1: one
// 2: two