用REGEX计算文本中的单词

Question

Hello :) I have to find all words in a given text with the following restrictions:

Matching should be case-insensitive. Not all matching substrings are words and should be counted. A word is a sequence of letters separated by punctuation or start/end of text. The output should be a single integer number.

I have already solved it with StringComparison and a for-loop.

The code below is my attempt to do it with REGEX(C#). It only gives me the count of the pattern word, but it is not aware for the restrictions.

Could you give me some tips on how to improve my REGEX pattern?

string patternWord = Console.ReadLine();
string[] inputSentence = Console.ReadLine().Split();
int count = 0;
string pattern = @"(?:\b\w+\ \s|\S)*" + patternWord + @"(?:\b\w+\b\ \s|\S)?";
Regex rx = new Regex(pattern, RegexOptions.IgnoreCase);
for (int i = 0; i < inputSentence.Length; i++)
{
    var mc = rx.Matches(inputSentence[i]);
    foreach (Match m in mc)
    {
        count++;
    }
}
Console.WriteLine("{0}", count);

EDIT:

Example:

Input word - hi

Input sentence - Hidden networks say only to Hitachi devices. , said Matuhi. !

I only need the bold ones.

EDIT 2: I have edited the restrictions as well.

Answer 1

How about a simple word-break regex?

\bhi\b

In C# this would be implemented like this:

private static int WordCount(string word, string text)
{
    var regex = new Regex(string.Format(@"\b{0}\b", word), 
                      RegexOptions.IgnoreCase);
    return regex.Matches(text).Count;
}

Answer 2

Sorry for not answering your exact questions, but why use regex? LINQ and a few utility methods from the Char class should suffice for this:

using System.Linq;

public class Test
{
    static void Main(string[] args)
    {
        string patternWord = Console.ReadLine();
        string inputSentence = Console.ReadLine();
        var words = GetWords(inputSentence);
        var count = words.Count(word => string.Equals(patternWord, word, StringComparison.InvariantCultureIgnoreCase));
        Console.WriteLine(count);
        Console.ReadLine();
    }

    private static IEnumerable<string> GetWords(string sentence)
    {
        while (!string.IsNullOrEmpty(sentence))
        {
            var word = new string(sentence.TakeWhile(Char.IsLetterOrDigit).ToArray());
            yield return word;
            sentence = new string(sentence.Skip(word.Length).SkipWhile(c => !Char.IsLetterOrDigit(c)).ToArray());
        }
    }
}