如何从.NET正则表达式中提取子字符串?

我想你想要

match.Groups[1].Value

(正如Dillie-O在评论中指出的,它是第1组,因为第0组总是整个匹配。)

简短但完整的测试程序:

using System;
using System.Text.RegularExpressions;

class Program
{
  static void Main()
  {
    Regex regex = new Regex("<key>LibID</key><val>([a-fA-F0-9]{4})</val>");
    Match match = regex.Match("Before<key>LibID</key><val>A67A</val>After");

    if (match.Success)
    {
      Console.WriteLine("Found Match for {0}", match.Value);
      Console.WriteLine("ID was {0}", match.Groups[1].Value);
    }      
  }
}

输出:

Found Match for <key>LibID</key><val>A67A</val>
ID was A67A

添加一个 grouping construct 你的表情…

<key>(?<id>LibID)</key><val>([a-fA-F0-9]{4})</val>

这将捕获ID。但是,您需要在表达式中为实际ID设置正确的格式,因为您的regex只捕获少量的“libid”。