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POIn .NET's RegEx can I get a Groups collection from a Capture object?
 

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  1. POIn .NET's RegEx can I get a Groups collection from a Capture object?
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    <p>.NET offers a Capture collection in its RegularExpression implementation so you can get all instances of a given repeating group rather than just the last instance of it. That's great, but I have a repeating group with <em>subgroups</em> and I'm trying to get at the subgroups as they are related under the group, and can't find a way. Any suggestions?</p> <p>I've looked at number of other questions, e.g.:</p> <ul> <li><a href="https://stackoverflow.com/questions/7187909/select-multiple-elements-in-a-regular-expression">Select multiple elements in a regular expression</a></li> <li><a href="https://stackoverflow.com/questions/5922683/regex-net-attached-named-group">Regex .NET attached named group</a></li> <li><a href="https://stackoverflow.com/questions/5930952/how-can-i-get-the-regex-groups-for-a-given-capture">How can I get the Regex Groups for a given Capture?</a></li> </ul> <p>but I have found no applicable answer either affirmative ("Yep, here's how") or negative ("Nope, can't be done.").</p> <p>For a contrived example say I have an input string:</p> <pre><code>abc d x 1 2 x 3 x 5 6 e fgh </code></pre> <p>where the "abc" and "fgh" represent text that I want to ignore in the larger document, "d" and "e" wrap the area of interest, and within that area of interest, "x n [n]" can repeat any number of times. It's those number pairs in the "x" areas that I'm interested in.</p> <p>So I'm parsing it using this regular expression pattern:</p> <pre><code>.*d (?&lt;x&gt;x ((?&lt;fir&gt;\d+) )?((?&lt;sec&gt;\d+) )?)*?e.* </code></pre> <p>which will find exactly one match in the document, but capture the "x" group many times. Here are the three pairs I would want to extract in this example:</p> <ul> <li>1, 2</li> <li>3</li> <li>5, 6</li> </ul> <p>but how can I get them? I could do the following (in C#): </p> <pre><code>using System; using System.Text; using System.Text.RegularExpressions; string input = "abc d x 1 2 x 3 x 5 6 e fgh"; string pattern = @".*d (?&lt;x&gt;x ((?&lt;fir&gt;\d+) )?((?&lt;sec&gt;\d+) )?)*?e.*"; foreach (var x in Regex.Match(input, pattern).Groups["x"].Captures) { MessageBox.Show(x.ToString()); } </code></pre> <p>and since I'm referencing group "x" I get these strings:</p> <ul> <li>x 1 2</li> <li>x 3</li> <li>x 5 6</li> </ul> <p>But that doesn't get me at the numbers themselves. So I could do "fir" and "sec" independently instead of just "x": </p> <pre><code>using System; using System.Text; using System.Text.RegularExpressions; string input = "abc d x 1 2 x 3 x 5 6 e fgh"; string pattern = @".*d (?&lt;x&gt;x ((?&lt;fir&gt;\d+) )?((?&lt;sec&gt;\d+) )?)*?e.*"; Match m = Regex.Match(input, pattern); foreach (var f in m.Groups["fir"].Captures) { MessageBox.Show(f.ToString()); } foreach (var s in m.Groups["sec"].Captures) { MessageBox.Show(s.ToString()); } </code></pre> <p>to get:</p> <ul> <li>1</li> <li>3</li> <li>5</li> <li>2</li> <li>6</li> </ul> <p>but then I have no way of knowing that it's the second pair that's missing the "4", and not one of the other pairs.</p> <p>So what to do? I know I could easily parse this out in C# or even with a second regex test on the "x" group, but since the first RegEx run has already done all the work and the results ARE known, it seems there ought to be a way to manipulate the Match object to get what I need out of it.</p> <p>And remember, this is a contrived example, the real world case is somewhat more complex so just throwing extra C# code at it would be a pain. But if the existing .NET objects can't do it, then I just need to know that and I'll continue on my way.</p> <p>Thoughts?</p>
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    1. COAppears there is no concept of hierarchy in names. I would just do a second Regex on x do get fir.
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