Use string.Replace to match whole words

Question

I\'m using NET 2.0 and WinForms.

Currently, I need a code to replace a string with another one in a given text, but in the text it should only look for whole words. What

Answer 1

string input = @"COUNTER = $40
CLOCK_COUNTER = $60";

string name = Regex.Replace(input, @"\bCOUNTER\b", "COUNT");

\b marks word boundries.

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The only alternative to Regex is to develop your own algorithm! Search for "COUNTER" and test the previous and following character for not being a word character.

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EDIT:

Here is my solution as extension method:

public static class ReplaceWordNoRegex
{
    private static bool IsWordChar(char c)
    {
        return Char.IsLetterOrDigit(c) || c == '_';
    }

    public static string ReplaceFullWords(this string s, string oldWord, string newWord)
    {
        if (s == null) {
            return null;
        }
        int startIndex = 0;
        while (true) {
            int position = s.IndexOf(oldWord, startIndex);
            if (position == -1) {
                return s;
            }
            int indexAfter = position + oldWord.Length;
            if ((position == 0 || !IsWordChar(s[position - 1])) && (indexAfter == s.Length || !IsWordChar(s[indexAfter]))) {
                s = s.Substring(0, position) + newWord + s.Substring(indexAfter);
                startIndex = position + newWord.Length;
            } else {
                startIndex = position + oldWord.Length;
            }
        }
    }
}

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EDIT #2: And here is a solution with StringBuilder.

public static string ReplaceFullWords(this string s, string oldWord, string newWord)
{
    if (s == null) {
        return null;
    }
    int startIndex = 0; // Where we start to search in s.
    int copyPos = 0; // Where we start to copy from s to sb.
    var sb = new StringBuilder();
    while (true) {
        int position = s.IndexOf(oldWord, startIndex);
        if (position == -1) {
            if (copyPos == 0) {
                return s;
            }
            if (s.Length > copyPos) { // Copy last chunk.
                sb.Append(s.Substring(copyPos, s.Length - copyPos));
            }
            return sb.ToString();
        }
        int indexAfter = position + oldWord.Length;
        if ((position == 0 || !IsWordChar(s[position - 1])) && (indexAfter == s.Length || !IsWordChar(s[indexAfter]))) {
            sb.Append(s.Substring(copyPos, position - copyPos)).Append(newWord);
            copyPos = position + oldWord.Length;
        }
        startIndex = position + oldWord.Length;
    }
}