从字符串中提取数字

string pat = "你好么123";
string str = Regex.Replace(pat, @"[^\d.\d]", "");
int result = 0;
if (Regex.IsMatch(str, @"^[+-]?\d*[.]?\d*$"))
{
    result = Convert.ToInt32(str);
}
//结果：result=123;