C# 如何用C来计算段落中某个单词的数量#

我试着写一个程序，用户给系统一个单词和一个段落，系统的任务是计算这个单词出现的次数

我如何计算这个词在C#中出现了多少次

这将：

• 通过检查每个字符（

  test.select

  ），将每个标点字符替换为一个空格，并将它们重新组合为另一个字符串（

  string.Concat

  ）
• 将字符串拆分为由空格分隔的子字符串（

  .Split

  ）
• 过滤掉，只保留与

  搜索

  字符串匹配的内容
• 计数它们

  Count（）

这将：

• 通过检查每个字符（

  test.select

  ），将每个标点字符替换为一个空格，并将它们重新组合为另一个字符串（

  string.Concat

  ）
• 将字符串拆分为由空格分隔的子字符串（

  .Split

  ）
• 过滤掉，只保留与

  搜索

  字符串匹配的内容
• 计数它们

  Count（）

正如文章所说的“<代码>对分割方法有一个性能开销。如果字符串上的唯一操作是对单词进行计数，则应该考虑使用匹配或索引方法而不是< /COD>”

因此，如果性能有问题，可以使用带有indexOf和count的while循环

class CountWords
{
    static void Main()
    {
        string text = @"Historically, the world of data and the world of objects" +
          @" have not been well integrated. Programmers work in C# or Visual Basic" +
          @" and also in SQL or XQuery. On the one side are concepts such as classes," +
          @" objects, fields, inheritance, and .NET Framework APIs. On the other side" +
          @" are tables, columns, rows, nodes, and separate languages for dealing with" +
          @" them. Data types often require translation between the two worlds; there are" +
          @" different standard functions. Because the object world has no notion of query, a" +
          @" query can only be represented as a string without compile-time type checking or" +
          @" IntelliSense support in the IDE. Transferring data from SQL tables or XML trees to" +
          @" objects in memory is often tedious and error-prone.";

        string searchTerm = "data";

        //Convert the string into an array of words 
        string[] source = text.Split(new char[] { '.', '?', '!', ' ', ';', ':', ',' }, StringSplitOptions.RemoveEmptyEntries);

        // Create the query.  Use ToLowerInvariant to match "data" and "Data"  
        var matchQuery = from word in source
                         where word.ToLowerInvariant() == searchTerm.ToLowerInvariant()
                         select word;

        // Count the matches, which executes the query. 
        int wordCount = matchQuery.Count();
        Console.WriteLine("{0} occurrences(s) of the search term \"{1}\" were found.", wordCount, searchTerm);

        // Keep console window open in debug mode
        Console.WriteLine("Press any key to exit");
        Console.ReadKey();
    }
}
/* Output:
   3 occurrences(s) of the search term "data" were found.
*/

正如文章所说的“<代码>对分割方法有一个性能开销。如果字符串上的唯一操作是对单词进行计数，则应该考虑使用匹配或索引方法而不是< /COD>”

因此，如果性能有问题，可以使用带有indexOf和count的while循环

class CountWords
{
    static void Main()
    {
        string text = @"Historically, the world of data and the world of objects" +
          @" have not been well integrated. Programmers work in C# or Visual Basic" +
          @" and also in SQL or XQuery. On the one side are concepts such as classes," +
          @" objects, fields, inheritance, and .NET Framework APIs. On the other side" +
          @" are tables, columns, rows, nodes, and separate languages for dealing with" +
          @" them. Data types often require translation between the two worlds; there are" +
          @" different standard functions. Because the object world has no notion of query, a" +
          @" query can only be represented as a string without compile-time type checking or" +
          @" IntelliSense support in the IDE. Transferring data from SQL tables or XML trees to" +
          @" objects in memory is often tedious and error-prone.";

        string searchTerm = "data";

        //Convert the string into an array of words 
        string[] source = text.Split(new char[] { '.', '?', '!', ' ', ';', ':', ',' }, StringSplitOptions.RemoveEmptyEntries);

        // Create the query.  Use ToLowerInvariant to match "data" and "Data"  
        var matchQuery = from word in source
                         where word.ToLowerInvariant() == searchTerm.ToLowerInvariant()
                         select word;

        // Count the matches, which executes the query. 
        int wordCount = matchQuery.Count();
        Console.WriteLine("{0} occurrences(s) of the search term \"{1}\" were found.", wordCount, searchTerm);

        // Keep console window open in debug mode
        Console.WriteLine("Press any key to exit");
        Console.ReadKey();
    }
}
/* Output:
   3 occurrences(s) of the search term "data" were found.
*/

---

将正则表达式与锚点一起使用：

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将正则表达式与锚点一起使用：

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可能的重复不是问题的重复-这是计算[英语]文本段落中的一个单词（而不是一个字符），具有不同的含义和解决方案。可能的重复不是问题的重复-这是计算[英语]文本段落中的一个单词（而不是一个字符）它有不同的含义和解决方案。您给出的示例使用Split（）方法。。。即使它说它不是更好的方法，并给出一个指向

Regex

Matches（）

方法的链接。。。split方法是错误的，因为它无法匹配上下文中的单词，例如

（word）

。的索引是错误的，因为它将匹配

notaword

@user2864740我不知道您是如何得出关于indexof的结论的。@使用简单indexof的浏览，如删除的答案中所示（此答案中暗示，甚至没有实现），并不能正确解释分词。因此，我的“结论”基于indexOf的一个同样不充分的隐含用法。。。即使它说它不是更好的方法，并给出一个指向

Regex

Matches（）

方法的链接。。。split方法是错误的，因为它无法匹配上下文中的单词，例如

（word）

。的索引是错误的，因为它将匹配

notaword

@user2864740我不知道您是如何得出关于indexof的结论的。@使用简单indexof的浏览，如删除的答案中所示（此答案中暗示，甚至没有实现），并不能正确解释分词。因此，我的“结论”基于indexOf同样不充分的隐含用法。

int wordCount = Regex.Matches(text, "\\b" + Regex.Escape(searchTerm) + "\\b", RegexOptions.IgnoreCase).Count;