c#提取字符串内某些数字

字符串
s1=klu-223x635x255
s2=ggh36%885%blj

需要提取得到
223
36

提取遇到的第一个完整数字串
string str = Regex.Match("klu-223x635x255", @"(\d+)").Groups[1].Value;

System.Text.RegularExpressions.Regex.Replace(string, @"[^0-9]+", "");

Regex reg = new Regex(@"(\s[+-]?\d+)([:])([\s])([\d])([.])([\d])([A-F]?)([+-]?)([\d])");
var d2 = s1.Matches(pkg);
var result = d2[0].value;