为什么我的{get; private set} 变量返回一个空字典？

Question

我正在尝试使用{get; private set;} 用于我正在构建的 MorseCode 翻译器。 MorseToText 词典应该是根据我已经定义的 TextToMorse 词典构建的。出于某种原因，我的词典在使用时是空的。

    private static Dictionary<char, string> TextToMorse = new Dictionary<char, string>()
    {
        {'A', ".-" }, {'B', "-..."}, {'C', "-.-."}, {'D', "-.."}, {'E', "."}, {'F', "..-."},
        {'G', "--."}, {'H', "...."}, {'I', ".."}, {'J', ".---"}, {'K', "-.-"}, {'L', ".-.."}, {'M', "--"},
        {'N', "-."}, {'O', "---"}, {'P', ".--."}, {'Q', "--.-"}, {'R', ".-."}, {'S', "..."}, {'T', "-"},
        {'U', "..-"}, {'V', "...-"}, {'W', ".--"}, {'X', "-..-"}, {'Y', "-.--"}, {'Z', "--.." }
    };

    private static Dictionary<string, char> _MorseToText = new Dictionary<string, char>();

    public static Dictionary<string, char> MorseToText
    {
        get { return _MorseToText; }

        private set
        {
            foreach (KeyValuePair<char, string> pair in TextToMorse)
            {
                _MorseToText.Add(pair.Value, pair.Key);
            }
        }
    }

...

        for (int i = 0; i < splitInput.Length; i++)
        {
            MorseToText.TryGetValue(splitInput[i], out char value);
            output += $"{value} ";
        }

Answer 1

你永远不会调用你的 setter，因此你的字典永远不会充满值。为了调用 setter，您必须编写例如MorseToText = new Dictionary<string,char>() 或例如MorseToText = null 在您的某处代码处。请注意，您输入 setter 的值将被丢弃。如果您调用 setter 两次，您的代码将抛出异常，因为您的字典已经包含键。这非常令人困惑，因此我建议使用静态构造函数。也许您还想使用只读字典来公开您的字典：

private static Dictionary<char, string> TextToMorse;
private static Dictionary<string, char> _MorseToText;

public static ReadOnlyDictionary<string,char> MorseToText {get; private set; }

static YourClassName()
{
    TextToMorse = new Dictionary<char, string>()
    {
        {'A', ".-" }, {'B', "-..."}, {'C', "-.-."}, {'D', "-.."}, {'E', "."}, {'F', "..-."},
        {'G', "--."}, {'H', "...."}, {'I', ".."}, {'J', ".---"}, {'K', "-.-"}, {'L', ".-.."}, {'M', "--"},
        {'N', "-."}, {'O', "---"}, {'P', ".--."}, {'Q', "--.-"}, {'R', ".-."}, {'S', "..."}, {'T', "-"},
        {'U', "..-"}, {'V', "...-"}, {'W', ".--"}, {'X', "-..-"}, {'Y', "-.--"}, {'Z', "--.." }
    };

    _MorseToText = new Dictionary<string,char>();
    foreach (KeyValuePair<char, string> pair in TextToMorse)
    {
        _MorseToText.Add(pair.Value, pair.Key);
    }
    MorseToText = new ReadOnlyDictionary(_MorseToText);
}

Answer 2

反转 Dictionary 的最简单方法之一是使用 ToDictionary linq 函数，然后交换 Key 和 Value:

static Dictionary<char, string> TextToMorse = new Dictionary<char, string>()
{
    {'A', ".-" }, {'B', "-..."}, {'C', "-.-."}, {'D', "-.."}, {'E', "."}, {'F', "..-."},
    {'G', "--."}, {'H', "...."}, {'I', ".."}, {'J', ".---"}, {'K', "-.-"}, {'L', ".-.."}, {'M', "--"},
    {'N', "-."}, {'O', "---"}, {'P', ".--."}, {'Q', "--.-"}, {'R', ".-."}, {'S', "..."}, {'T', "-"},
    {'U', "..-"}, {'V', "...-"}, {'W', ".--"}, {'X', "-..-"}, {'Y', "-.--"}, {'Z', "--.." }
};
static Dictionary<string, char> MorseToText = TextToMorse.ToDictionary(x => x.Value, x => x.Key);

目前您使用的setter有误。当您为 MorseToText 赋值时，将调用 set 函数。例如，当您尝试将 MorseToText 设置为 MorseToText = null 等任何实例时，它将运行覆盖您使用 setter.[=18 中的代码期望的默认行为=]

为什么我的{get; private set} 变量返回一个空字典？

Why is my {get; private set} variable returning an empty Dictionary?

c#

dictionary

morse-code