public static void Main()
var input = "#define IP \"127.0.0.1\"";
var replacement = "4.4.4.4";
var rgx = new System.Text.RegularExpressions.Regex(@"\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}");
string result = rgx.Replace(input, replacement);
Console.WriteLine(result);
input = "#define IP \"8.8.8.8\"";
rgx = new System.Text.RegularExpressions.Regex(@"\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}");
result = rgx.Replace(input, replacement);
Console.WriteLine(result);
input = "#define IP \"192.168.1.1\"";
rgx = new System.Text.RegularExpressions.Regex(@"\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}");
result = rgx.Replace(input, replacement);
Console.WriteLine(result);