分組構造描述正則運算式的子運算式並捕獲輸入字串的子字串。下表列出了分組結構：
| 分組結構 | 描述 | 模式 | 匹配 |
|---|---|---|---|
( subexpression ) |
捕獲匹配的子運算式，並將其分配為從零開始的序數 | (\w)\1 |
"ee"匹配"deep" |
(?< name >subexpression) |
將匹配的子運算式捕獲到命名組中 | (?< double>\w)\k< double> |
"ee"匹配"deep" |
(?< name1 -name2 >subexpression) |
定義平衡組定義 | (((?'Open'\()[^\(\)]*)+((?'Close-Open'\))[^\(\)]*)+)*(?(Open)(?!))$ |
"((1-3)*(3-1))"匹配"3+2^((1-3)*(3-1))" |
(?: subexpression) |
定義非捕獲組 | Write(?:Line)? |
"WriteLine" 匹配"Console.WriteLine()" |
(?imnsx-imnsx:subexpression) |
在子運算式中應用或禁用指定的選項 | A\d{2}(?i:\w+)\b |
"A12xl", "A12XL" 匹配 "A12xl A12XL a12xl" |
(?= subexpression) |
零寬正向前瞻斷言 | \w+(?=\.) |
"is", "ran", 和 "out" 匹配 "He is. The dog ran. The sun is out." |
(?! subexpression) |
零寬度負向前瞻斷言 | \b(?!un)\w+\b |
"sure", "used" 匹配 "unsure sure unity used" |
(?< =subexpression) |
零寬度正向後斷言 | (?< =19)\d{2}\b |
"51", "03" 匹配 "1851 1999 1950 1905 2003" |
(?< ! subexpression) |
零寬度負向後斷言 | (?< !19)\d{2}\b |
"ends", "ender" 匹配 "end sends endure lender" |
(?> subexpression) |
非追溯(或“貪懶”)子運算式 | [13579](?>A+B+) |
"1ABB", "3ABB" 和 "5AB" 匹配 "1ABB 3ABBC 5AB 5AC" |