How to properly access the value of a capture group in C# regex?

Question

I have the following code:

using System;
using System.Text.RegularExpressions;

public class Test
{
   public static void Main()
   {
      var r = new Regex(@"_(\d+)$");
      string new_name = "asdf_1";

      new_name = r.Replace(new_name, match =>
      {
         Console.WriteLine(match.Value);
         return match.Value;
         //return (Convert.ToUInt32(match.Value) + 1).ToString();
      });

      //Console.WriteLine(new_name);
   }
}

I expect match.Value to be 1, but it is printing as _1. What am I doing wrong?

@Selman22 I can't, the `_` is an important delimiter and I need to check for it. The point is, the `_` isn't in the capture group so it shouldn't show up. I want to make it work with the `_` as it is. — void.pointer, Jan 06 '15 at 16:05
`match.Value` is the entire match. Use match.Groups[1].Value. — , Jan 06 '15 at 17:43

score 5 · Accepted Answer · answered Jan 06 '15 at 16:06

5

You're getting the value of the whole Match - you only want a single group (group 1) which you can access via the Groups property and the GroupCollection indexer:

Console.WriteLine(match.Groups[1]);

answered Jan 06 '15 at 16:06

Jon Skeet

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I was trying the same with `match.Captures`, I am not sure of the difference. – void.pointer Jan 06 '15 at 16:06
@void.pointer: I believe the point of `Captures` is when a single group has multiple captures. – Jon Skeet Jan 06 '15 at 16:09
Apparently [I'm not the only one who's confused](http://stackoverflow.com/questions/3320823/whats-the-difference-between-groups-and-captures-in-net-regular-expression). Thanks for your help! This works great. – void.pointer Jan 06 '15 at 16:10

How to properly access the value of a capture group in C# regex?

1 Answers1