Question

我想遍历字典值，该值是C＃中的字符串列表，以检查所有键

Dictionary<string, List<string>> csvList = new Dictionary<string, List<string>>();

我想检查csvList中的每个键（字符串），并检查它是否存在于任何值（列表）中

foreach(var events in csvList)
{
   foreach(var action in csvList.Values) // But I want to loop through all the lists in dictionary, not just the list of event key
    {
    }
}

Answer 1

这有点奇怪，但让我们尝试解决它。我们通常不希望迭代字典的键。使用其中一个的原因是，如果我们已经知道密钥，我们希望很快获得值。

本着回答问题的精神，要遍历Dictionary的键，必须使用Keys属性。请注意，不能保证与此集合的顺序有关。

var d = new Dictionary<string, int>();
d.Add("one", 1);
d.Add("two", 2);

foreach (var k in d.Keys) {
    Console.WriteLine(k);
}

但是我认为您可能有问题，选择了Dictionary作为解决方案，然后在无法解决问题时来到这里。如果字典不是问题怎么办？

听起来您有多个List<string>实例，并且您对特定列表是否包含特定字符串感兴趣。也许您想知道，“哪个列表包含哪个字符串？”我们可以用略有不同的字典来回答这个问题。我将使用数组而不是列表，因为它更容易键入。

using System;
using System.Collections.Generic;

public class Program
{
    private static void AddWord(Dictionary<string, List<int>> d, string word, int index) {
        if (!d.ContainsKey(word)) {
            d.Add(word, new List<int>());   
        }

        d[word].Add(index);
    }

    private static List<int> GetIndexesForWord(Dictionary<string, List<int>> d, string word) {
        if (!d.ContainsKey(word)) {
            return new List<int>();
        } else {
            return d[word];
        }
    }

    public static void Main()
    {
        var stringsToFind = new[] { "one", "five", "seven" };

        var listsToTest = new[] {
            new[] { "two", "three", "four", "five" },
            new[] { "one", "two", "seven" },
            new[] { "one", "five", "seven" }
        };

        // Build a lookup that knows which words appear in which lists, even
        // if we don't care about those words.
        var keyToIndexes = new Dictionary<string, List<int>>();
        for (var listIndex = 0; listIndex < listsToTest.GetLength(0); listIndex++) {
            var listToTest = listsToTest[listIndex];
            foreach (var word in listToTest) {
                AddWord(keyToIndexes, word, listIndex);
            }
        }

        // Report which lists have the target words.
        foreach (var target in stringsToFind) {
            Console.WriteLine("Lists with '{0}':", target);
            var indices = GetIndexesForWord(keyToIndexes, target);
            if (indices.Count == 0) {
                Console.WriteLine("  <none>");
            } else {
                var message = string.Join(", ", indices);
                Console.WriteLine("  {0}", message);
            }
        }
    }
}

Answer 2

foreach(var events in csvList)
{
   foreach(var action in csvList.Values) 
    {
       if (action.Contains(events.Key)) //Just use this, there is no point to iterate the list as you can use contains method
    }
}

遍历C＃中的字典值列表以检查特定键

2 个答案: