c#分类列表<；字符串，TValue>；。成功添加密钥的ContainsKey返回false

检查下面的更新3 我发现我遇到的问题与.Net 4.0、4.0客户端和4.5的c#字符串比较器的一个已知严重问题有关，这将导致字符串列表的排序顺序不一致（导致输出取决于输入的顺序和使用的排序算法）。该问题于2012年12月报告给微软，并以“不会被修复”而关闭。有一种变通方法可用，但速度太慢，难以用于大型收藏

在实现不可变的PatriciaTrie时，我想将其性能与System.Collections.Generic.SortedList进行比较。我使用以下文件创建了一个用于测试的输入字列表

使用

Comparer.Default

或

StringComparer.InvariantCulture

作为键比较器，在c#SortedList中插入每个单词时，无法使用常规搜索方法检索成功插入的许多条目（例如

ContainsKey

返回false）但是，正如通过迭代列表所观察到的那样，该键存在于列表中

更奇怪的是，当比较从排序列表检索到的键与使用

ContainsKey

无法找到的搜索键时，比较器返回值“0”

下面的完整示例在我的系统上演示了此问题

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

class Program
{
    static void Main(string[] args)
    {
        // the problem is possibly related to comparison.
        var fail = true;
        var comparer = fail ? StringComparer.InvariantCulture : StringComparer.Ordinal;

        // read hamlet (contains duplicate words)
        var words = File
            .ReadAllLines("hamlet.txt")
            .SelectMany(l => l.Split(new[] { ' ', '\t' }, StringSplitOptions.RemoveEmptyEntries))
            .Select(w => w.Trim())
            .Where(w => !string.IsNullOrEmpty(w))
            .Distinct(comparer)
            .ToArray();

        // insert hamlet's words in the sorted list.
        var list = new SortedList<string, int>(comparer);
        var ndx = 0;
        foreach (var word in words)
            list[word] = ndx++;

        // search for each of the added words.
        foreach (var keyToSearch in words)
        {
            if (!list.ContainsKey(keyToSearch))
            {
                // was inserted, but cannot be retrieved.
                Console.WriteLine("Error - Key not found: \"{0}\"", keyToSearch);
                // however when we iterate over the list, we see that the entry is present
                var prefix = keyToSearch.Substring(0, Math.Min(keyToSearch.Length, 3));
                foreach (var wordCloseToSearchKey in list.Keys.Where(s => s.StartsWith(prefix)))
                {
                    // and using the SortedList's supplied comparison returns 0, signaling equality
                    var comparisonResult = list.Comparer.Compare(wordCloseToSearchKey, keyToSearch);
                    Console.WriteLine("{0} - comparison result = {1}", wordCloseToSearchKey, comparisonResult);
                }
            }
        }

        // Check that sort order of List.Keys is correct 
        var keys = list.Keys.ToArray();
        BinarySearchAll("list.Keys", keys, list.Comparer);
        CheckCorrectSortOrder("list.Keys", keys, list.Comparer);

        // Check that sort order of Array.Sort(List.Keys) is correct 
        var arraySortedKeys = CopySortSearchAndCheck("Array.Sort(List.Keys)", keys, list.Comparer);

        // Check that sort order of the Array.Sort(input words) is correct 
        var sortedInput = CopySortSearchAndCheck("Array.Sort(input words)", words, list.Comparer);

        Console.ReadLine();
    }

    static string[] CopySortSearchAndCheck(string arrayDesc, string[] input, IComparer<string> comparer)
    {
        // copy input
        var sortedInput = new string[input.Length];
        Array.Copy(input, sortedInput, sortedInput.Length);

        // sort it
        Array.Sort(sortedInput, comparer);

        // check that we can actually find the keys in the array using bin. search
        BinarySearchAll(arrayDesc, sortedInput, comparer);

        // check that sort order is correct
        CheckCorrectSortOrder(arrayDesc, sortedInput, comparer);

        return sortedInput;
    }

    static void BinarySearchAll(string arrayDesc, string[] sortedInput, IComparer<string> comparer)
    {
        // check that each key in the input can be found using bin. search
        foreach (var word in sortedInput)
        {
            var ix = Array.BinarySearch(sortedInput, word, comparer);
            if (ix < 0)
                // and it appears it cannot!
                Console.WriteLine("Error - {0} - Key not found: \"{1}\"", arrayDesc, word);
        }
    }

    static void CheckCorrectSortOrder(string arrayDesc, string[] sortedKeys, IComparer<string> comparer)
    {
        for (int n = 0; n < sortedKeys.Length; n++)
        {
            for (int up = n + 1; up < sortedKeys.Length; up++)
            {
                var cmp = comparer.Compare(sortedKeys[n], sortedKeys[up]);
                if (cmp >= 0)
                {
                    Console.WriteLine(
                        "{0}[{1}] = \"{2}\" not < than {0}[{3}] = \"{4}\"  - cmp = {5}",
                        arrayDesc, n, sortedKeys[n], up, sortedKeys[up], cmp);
                }
            }
            for (int down = n - 1; down > 0; down--)
            {
                var cmp = comparer.Compare(sortedKeys[n], sortedKeys[down]);
                if (cmp <= 0)
                {
                    Console.WriteLine(
                        "{0}[{1}] = \"{2}\" not > than {0}[{3}] = \"{4}\"  - cmp = {5}",
                        arrayDesc, n, sortedKeys[n], down, sortedKeys[down], cmp);
                }
            }
        }
    }
}

这是它的输出：

a1 < a2   (A < a')
a2 < a3   (a' < 'a)
a1 > a3   (A > 'a)

---

所以我仍然希望微软重新考虑，或者有人知道一个可行的替代方案。否则，剩下的唯一选项就是使用

StringComparer.Ordinal

它是否与.Net Framework 4/4.5相关？我已将您的示例改编为.Net 3.5，如下所示：

var words = ReadFile("hamlet.txt");

//...

private static string[] ReadFile(string path)
{
    List<string> lines = new List<string>();
    using (StreamReader sr = new StreamReader(path))
    {
        string text = sr.ReadToEnd();
        lines.Add(text);
    }

    return lines.SelectMany(l => l.Split(new[] { ' ', '\t' }, StringSplitOptions.RemoveEmptyEntries).Select(w => w.Trim()))
        .Where(w => !(w.ToCharArray().All(c => c == ' ')))
        .ToArray();
}

var words=ReadFile（“hamlet.txt”）；
//...
私有静态字符串[]读取文件（字符串路径）
{
列表行=新列表（）；
使用（StreamReader sr=新StreamReader（路径））
{
string text=sr.ReadToEnd（）；
行。添加（文本）；
}
返回行。SelectMany（l=>l.Split（new[]{''，'\t'}，StringSplitOptions.RemoveEmptyEntries）。选择（w=>w.Trim（））
.Where（w=>！（w.ToCharArray（）.All（c=>c=''））
.ToArray（）；
}

---

使用.Net 3.5时，两个比较器在XP上都能正常工作。

确认：在同一系统上使用.Net 3.5和.Net 3.5客户端配置文件时，不会出现问题。4.0、4.0客户端和4.5都有相同的问题。我排除了更多的故障，并确认

Array.BinarySearch

显示了相同的问题。信息添加到原始问题中。使用此新信息，似乎这是一个已知问题：请参阅并链接到已报告（已关闭）的问题有趣的是，Marc Gravell在2006年为.Net 2.0报告了相同/类似的问题，也以“不会修复”结束。可能在3.5中固定，在4.0中回归？不是100%反对称的比较器有什么实际用途吗？我可以想象使用比较器来定义偏序（如果

a>b

和

b>c

，并且

a

和

c

有一个定义的秩，那么

a>c

），但是对于

a>b

和

b>a

都可能为真的比较器，没有一个比较器是这样的。

public class WorkAroundStringComparer : StringComparer
{
    private static readonly Func<CompareInfo, string, CompareOptions, int> _getHashCodeOfString;
    private readonly CompareInfo _compareInfo;
    private readonly CompareOptions _compareOptions;

    static WorkAroundStringComparer()
    {
        // Need this internal method to compute hashcode
        // as an IEqualityComparer implementation.
        _getHashCodeOfString = BuildGetHashCodeOfStringDelegate();
    }

    static Func<CompareInfo, string, CompareOptions, int> BuildGetHashCodeOfStringDelegate()
    {
        var compareInfoType = typeof(CompareInfo);
        var argTypes = new[] { typeof(string), typeof(CompareOptions) };
        var flags = BindingFlags.NonPublic | BindingFlags.Instance;
        var methods = compareInfoType.GetMethods(flags).ToArray(); ;
        var method = compareInfoType.GetMethod("GetHashCodeOfString", flags, null, argTypes, null);

        var instance = Expression.Parameter(compareInfoType, "instance");
        var stringArg = Expression.Parameter(typeof(string), "string");
        var optionsArg = Expression.Parameter(typeof(CompareOptions), "options");
        var methodCall = Expression.Call(instance, method, stringArg, optionsArg);
        var expr = Expression.Lambda<Func<CompareInfo, string, CompareOptions, int>>(methodCall, instance, stringArg, optionsArg);
        return expr.Compile();
    }

    public WorkAroundStringComparer()
        : this(CultureInfo.InvariantCulture)
    {
    }

    public WorkAroundStringComparer(CultureInfo cultureInfo, CompareOptions compareOptions = CompareOptions.None)
    {
        if (cultureInfo == null)
            throw new ArgumentNullException("cultureInfo");
        this._compareInfo = cultureInfo.CompareInfo;
        this._compareOptions = compareOptions;
    }

    public override int Compare(string x, string y)
    {
        if (ReferenceEquals(x, y))
            return 0;
        if (ReferenceEquals(x, null))
            return -1;
        if (ReferenceEquals(y, null))
            return 1;

        var sortKeyFor_x = _compareInfo.GetSortKey(x, _compareOptions);
        var sortKeyFor_y = _compareInfo.GetSortKey(y, _compareOptions);
        return SortKey.Compare(sortKeyFor_x, sortKeyFor_y);
    }

    public override bool Equals(string x, string y)
    {
        return Compare(x, y) == 0;
    }

    public override int GetHashCode(string obj)
    {
        return _getHashCodeOfString(_compareInfo, obj, _compareOptions);
    }
}

StringComparer.InvariantCulture : 00:00:15.3120013
WorkAroundStringComparer        : 00:01:35.8322409

var words = ReadFile("hamlet.txt");

//...

private static string[] ReadFile(string path)
{
    List<string> lines = new List<string>();
    using (StreamReader sr = new StreamReader(path))
    {
        string text = sr.ReadToEnd();
        lines.Add(text);
    }

    return lines.SelectMany(l => l.Split(new[] { ' ', '\t' }, StringSplitOptions.RemoveEmptyEntries).Select(w => w.Trim()))
        .Where(w => !(w.ToCharArray().All(c => c == ' ')))
        .ToArray();
}