In C#, how can I use Regex.Replace to add leading zeroes (if possible)?

Question

I would like to add a certain number of leading zeroes to a number in a string. For example:

Input: \"page 1\", Output: \"page 001\" Input: \"page 12\", Ouput: \"pa

Answer 1

string sInput = "page 1";
//sInput = Regex.Replace(sInput, @"\d+", @"00$&");
string result = Regex.Replace(sInput, @"\d+", me =>
{
    return int.Parse(me.Value).ToString("000");
});