如何根据特定的键检查值？

Question

我目前正在努力学习字典是如何工作的，但我找不到怎么做标题上说的。

using System;
using System.Collections.Generic;

namespace Demo.Aiman1
{
    class Program
    {
        static void Main(string[] args)
        {
            Dictionary<string, string> guestsFoods = new Dictionary<string, string>();
            guestsFoods.Add("Fiora", "Pancakes");
            guestsFoods.Add("Darius", "Pancakes");
            guestsFoods.Add("Mordekaiser", "Apple");
            if (guestsFoods.ContainsValue("Pancakes"))
            {
                Console.WriteLine("Something");
            }
        }
    }
}

现在，代码正在检查字典值部分中的字符串“Pancake”是否存在。我想要的是，要检查字典的第一个键(在当前情况下是“Fiora”)，是否有字符串“Pancake”。

Answer 1

        Dictionary<string, string> guestsFoods = new Dictionary<string, string>();
        guestsFoods.Add("Fiora", "Pancakes");
        guestsFoods.Add("Darius", "Pancakes");
        guestsFoods.Add("Mordekaiser", "Apple");
        foreach (var kvp in guestsFoods)
        {
            if (kvp.Value== "Pancakes")
            {
                Console.WriteLine($"{kvp.Key}");
                break;
            }
        }

嗨，希望这能解决你的问题！

Answer 2

您可能需要考虑ToLookup，然后可以这样做：

var guestsFoods = new Dictionary<string, string>()
{
    { "Fiora", "Pancakes"},
    { "Darius", "Pancakes"},
    { "Mordekaiser", "Apple"},
};

var opposite = guestsFoods.ToLookup(x => x.Value, x => x.Key);

if (opposite.Contains("Pancakes"))
{
    Console.WriteLine(String.Join(", ", opposite["Pancakes"]));
}

输出Fiora, Darius。