How to detect which numbers are in a string in C#?

  //测试函数
        private void Form1_Load(object sender, EventArgs e)
        {
            foreach (var number in ExtractNumbersFromString("abc2345 345fdf678 jdhfg945"))
            {
                MessageBox.Show(number.ToString());
            }
        }

        private IEnumerable<int> ExtractNumbersFromString(string s)
        {
            //Regex.Matches 方法：在输入字符串中搜索正则表达式的所有匹配项并返回所有匹配。
            //一次或多次匹配前面的字符或子表达式。等效于 {1,}。如果将+去掉，就是
            //return Regex.Matches(s, @"\d+").Cast<Match>().Select(m => Convert.ToInt32(m.Value));
            return Regex.Matches(s, @"\d").Cast<Match>().Select(m => Convert.ToInt32(m.Value));
        }

2345  
345
678
945

2
3
4
5
3
.......