C# 3.0 Cookbook, 3rd Edition

10.2. Extracting Groups from a MatchCollection

Problem

You have a regular expression that contains one or more named groups, such as the following:

	\\\\(?<TheServer>\w*)\\(?<TheService>\w*)\\

where the named group TheServer will match any server name within a UNC string, and TheService will match any service name within a UNC string.

Tip

This pattern does not match the UNCW format.

You need to store the groups that are returned by this regular expression in a keyed collection (such as a Dictionary<string, Group>) in which the key is the group name.

Solution

The ExtractGroupings method shown in Example 10-3 obtains a set of Group objects keyed by their matching group name.

Example 10-3. ExtractGroupings method

using System;
using System.Collections;
using System.Collections.Generics;
using System.Text.RegularExpressions;

public static List<Dictionary<string, Group>> ExtractGroupings(string source
                                                           string matchPattern,
                                                           bool wantInitialMatch)
{
    List<Dictionary<string, Group>> keyedMatches = 
        new List<Dictionary<string, Group>>();
    int startingElement = 1;
    if (wantInitialMatch)
    {
        startingElement = 0;
    }

    Regex RE = new Regex(matchPattern, RegexOptions.Multiline);
    MatchCollection theMatches = RE.Matches(source);

    foreach(Match m in theMatches)
    {
        Dictionary<string, Group> groupings = new Dictionary<string, Group>();

        for (int counter = startingElement; counter < m.Groups.Count; counter++) { // If we had just returned the MatchCollection directly, the // GroupNameFromNumber method would not be available ...