C#代码的Regex的Repalce方法怎么将字符串替换为子串

Question

C#代码的Regex的Repalce方法怎么将字符串替换为子串：比如abc123abc替换为123string pattern = @"\w+(\d+)\w+";Regex rg = new Regex(pattern);string result = rg.Replace("abc123abc","$1");想得到的结果result:123,但是result:3，怎么做才正确