private static async Task<List<string>> createTxt()
{
    // 確保目錄存在
    if (!Directory.Exists(DEFAULT_PATH))
        Directory.CreateDirectory(DEFAULT_PATH);

    while (true)
    {
        Console.Write("Please input text type as you want, you can input more:>>>");
        string? input = Console.ReadLine();
        if (string.IsNullOrWhiteSpace(input)) continue;

        string[] filesName = input.Split(',', StringSplitOptions.RemoveEmptyEntries)
                                  .Select(s => s.Trim())
                                  .ToArray();
        var textList = new List<Task<string>>();

        foreach (string text in filesName)
        {
            if (!parityText(text)) continue;               // 文件名校驗
            if (File.Exists(Path.Combine(DEFAULT_PATH, text)))
            {
                Console.WriteLine("File is Existing");
                continue;
            }
            textList.Add(createAsyncFile(text));           // 每個文件一個異步任務
        }

        if (textList.Count == 0) continue;

        string[] files = await Task.WhenAll(textList);     // 并發(fā)等待所有文件創(chuàng)建完成
        List<string> fileList = files.Where(f => f != null)
                                     .Select(f => Path.Combine(DEFAULT_PATH, f))
                                     .ToList();
        Console.WriteLine($"所有文件創(chuàng)建完成，共 {textList.Count} 個。");
        return fileList;
    }
}

private static async Task<string> createAsyncFile(string text)
{
    try
    {
        string default_content = $"http:// Created:{DateTime.Now:yyyy-MM-dd HH:mm:ss} \n// Author: Dong Wang  ";
        await File.WriteAllTextAsync(Path.Combine(DEFAULT_PATH, text), default_content);
        lock (_lock) Console.WriteLine($"Created successfully!!!! File Name:{text}");
        return text;
    }
    catch (Exception ex)
    {
        lock (_lock) Console.WriteLine($"{ex.Message}");
        return null;
    }
}

private static Dictionary<string, int> GetTextsFromFile(string fileReal)
{
    string text = File.ReadAllText(Path.Combine(DEFAULT_PATH, fileReal)).ToLower();
    // 按非單詞字符分割（空格、標點、換行等）
    string[] words = Regex.Split(text, @"\W+");
    var wordCount = new Dictionary<string, int>();
    foreach (string w in words)
    {
        if (string.IsNullOrEmpty(w)) continue;
        string word = w.ToLower();
        if (wordCount.ContainsKey(word))
            wordCount[word]++;
        else
            wordCount[word] = 1;
    }
    return wordCount;
}

var tasks = filesReal.Select(async filePath =>
{
    var wordCount = await Task.Run(() => GetTextsFromFile(filePath));
    return (FileName: Path.GetFileName(filePath), WordCount: wordCount);
});
var results = await Task.WhenAll(tasks);
var textWords = results.ToDictionary(r => r.FileName, r => r.WordCount);

Dictionary<string, Dictionary<string, int>> textWords = 
    new Dictionary<string, Dictionary<string, int>>(StringComparer.OrdinalIgnoreCase);

private static void UserInputQueryWord(string v, Dictionary<string, Dictionary<string, int>> textwords)
{
    while (true)
    {
        Console.Write("Please input query word:>>");
        string? input = Console.ReadLine();
        if (input == null) continue;
        input = input.ToLower();
        string[] words = SplitWord(input);
        foreach (string word in words)
        {
            if (textwords.TryGetValue(v, out var wordCount) &&
                wordCount.TryGetValue(word, out int count))
            {
                Console.WriteLine($"該文件 {v} 中的搜索詞 {word} 查詢出現(xiàn)的頻率: {count} 次");
            }
            else
            {
                Console.WriteLine($"該文件 {v} 中的搜索詞 {word} 未找到");
            }
        }
        break;
    }
}

Please input text type as you want, you can input more:>>>a.txt, b.txt
Created successfully!!!! File Name:a.txt
Created successfully!!!! File Name:b.txt
所有文件創(chuàng)建完成，共 2 個。
是否需要為該文件:...\a.txt，寫入內(nèi)容？Y/N:>>y
請輸入你要往...\a.txt 文件傳輸?shù)膬?nèi)容:>>hello world hello C# is powerful
文件...\a.txt，成功被寫入
是否需要為該文件:...\b.txt，寫入內(nèi)容？Y/N:>>n
用戶不進行寫入，該文件：...\b.txt
Please input the specify file:>a.txt
1 words
文件名:a.txt
Please input query word:>>hello
該文件 a.txt 中的搜索詞 hello 查詢出現(xiàn)的頻率: 2 次
是否退出？(Y/N)::>>y
CreateTxt Method is Done