如何在空格上匹配正则表并在不覆盖空格的情况下进行替换

Question

I have a Regex match like the following code:

string[] specials = new string[] { "special1", "special2", "special3" };
for (int i = 0; i < specials.Length; i++)
{
    string match = string.Format("(?:\\s)({0})(?:\\s)", specials[i]);
    if (Regex.IsMatch(name, match, RegexOptions.IgnoreCase))
    {
        name = Regex.Replace(name, match, specials[i], RegexOptions.IgnoreCase);
        break;
    }
}

What I would like is to have the replace operation replace only the matching text and leave the leading and trailing space in tact. So "This is a Special1 sentence" would become "This is a special1 sentence". With the Replace statement above I get "This is aspecial1sentence".

Solution:

Based on @Jerry's comment, I changed the match to:

(\\\\s)({0})(\\\\s)

and the Replace to:

name = Regex.Replace(name, match, "$1" + specials[i] + "$3", RegexOptions.IgnoreCase);

and was able to get the desired results.

Answer 1

You can use a lookbehind and a lookahead to check for the spaces without including them in the match:

string[] specials = new string[] { "special1", "special2", "special3" };
for (int i = 0; i < specials.Length; i++)
{
    string match = string.Format("(?<=\\s){0}(?=\\s)", specials[i]);
    if (Regex.IsMatch(name, match, RegexOptions.IgnoreCase))
    {
        name = Regex.Replace(name, match, specials[i], RegexOptions.IgnoreCase);
        break;
    }
}

This way you don't have to add the spaces back in.