C # Regex group Group "Go"

http://www.cnblogs.com/kiant71/archive/2010/08/14/1799799.html

In a regular expression, if you want to extract several different parts (sub-expression items), you need to use the grouping feature.

In C # regular expressions, the Regex membership is as follows, where group is its grouping processing class.

Regex–> matchecollection (Match item collection)

–> Match (single match content)

–> GroupCollection (the "(Group/Sub-expression Items)" collection contained in a single match)

–> Group ("(Group/Sub-expression items)" content)

–> caputercollection (Group item content display basis?) )

–> Caputer

Group has two access methods for grouping:

1. Array subscript Access

In ((\d+) ([A-z]) \s+ This regular expression contains a total of four groupings, according to the default left-to-right matching method,

Groups[0] represents the match itself, which is the entire expression ((\d+) ([A-z]) \s+

GROUPS[1] Represents the sub-expression item ((\d+) ([A-z])

GROUPS[2] Represents a sub-expression item (\d+)

GROUPS[3] Represents the sub-expression item ([A-z])

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stringtext = "1A 2B 3C 4D 5E 6F 7G 8H 9I 10J 11Q 12J 13K 14L 15M 16N ffee80 #800080";Response.Write(text + "<br/>");stringstrPatten = @"((\d+)([a-z]))\s+";Regex rex = newRegex(strPatten, RegexOptions.IgnoreCase);MatchCollection matches = rex.Matches(text);//提取匹配项foreach(Match match inmatches){    GroupCollection groups = match.Groups;    Response.Write(string.Format("<br/>{0} 共有 {1} 个分组：{2}<br/>"                                , match.Value, groups.Count, strPatten));    //提取匹配项内的分组信息    for(inti = 0; i < groups.Count; i++)    {        Response.Write(            string.Format("分组 {0} 为 {1}，位置为 {2}，长度为 {3}<br/>"                        , i                        , groups[i].Value                        , groups[i].Index                        , groups[i].Length));    }}/*  * 输出： 1A 2B 3C 4D 5E 6F 7G 8H 9I 10J 11Q 12J 13K 14L 15M 16N ffee80 #8000801A 共有 4 个分组：((\d+)([a-z]))\s+分组 0 为 1A ，位置为 0，长度为 3分组 1 为 1A，位置为 0，长度为 2分组 2 为 1，位置为 0，长度为 1分组 3 为 A，位置为 1，长度为 1  ....  */

2. Named access

Use (?<xxx> subexpression) to define a grouping alias so that you can access the group/subexpression content using groups["XXX".

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stringtext = "I‘ve found this amazing URL at http://www.sohu.com, and then find ftp://ftp.sohu.comisbetter.";Response.Write(text + "<br/>");stringpattern = @"\b(?<protocol>\S+)://(?<address>\S+)\b";Response.Write(pattern.Replace("<", "&lt;").Replace(">","&gt;") + "<br/><br/>");MatchCollection matches = Regex.Matches(text, pattern);foreach(Match match inmatches){    GroupCollection groups = match.Groups;    Response.Write(string.Format(                    "URL: {0}； Protocol: {1}； Address: {2} <br/>"                    , match.Value                    , groups["protocol"].Value                     , groups["address"].Value));}/*  * 输出 I‘ve found this amazing URL at http://www.sohu.com, and then find ftp://ftp.sohu.comisbetter.    \b(?<protocol>\S+)://(?<address>\S+)\b     URL: http://www.sohu.com； Protocol: http； Address: www.sohu.com     URL: ftp://ftp.sohu.comisbetter； Protocol: ftp； Address: ftp.sohu.comisbetter  */

Content reference from:

C # Regular expression programming (iii): Match class and group class usage http://blog.csdn.net/zhoufoxcn/archive/2010/03/09/5358644.aspx

C # Regular expression class match and group class understanding http://tech.ddvip.com/2008-10/122483707982616.html

C # Regex group Group "Go"