規則運算式類別
下列章節說明 .NET Framework 規則運算式類別。
Regex
Regex 類別表示不變的 (唯讀) 規則運算式。它也包含靜態方法，允許使用其他規則運算式類別，而不需明確建立其他類別的執行個體。
下列程式碼範例建立 Regex 類別的執行個體，並在物件初始化時定義簡單規則運算式。請注意將額外反斜線當做逸出字元的用法，表示在 \s 比對字元類別中的反斜線為常值字元。
' Declare object variable of type Regex.
Dim r As Regex
' Create a Regex object and define its regular expression.
r = New Regex("\s2000")
// Declare object variable of type Regex.
Regex r;
// Create a Regex object and define its regular expression.
r = new Regex("\\s2000");
Match
Match 類別表示規則運算式比對作業的結果。下列範例使用 Regex 類別的 Match 方法，傳回 Match 型別的物件，以便尋找輸入字串中的第一個相符比對。範例使用 Match 類別的 Match.Success 屬性，指示是否找到相符比對。
' cCreate a new Regex object.
Dim r As New Regex("abc")
' Find a single match in the input string.
Dim m As Match = r.Match("123abc456")
If m.Success Then
' Print out the character position where a match was found.
' (Character position 3 in this case.)
Console.WriteLine("Found match at position " & m.Index.ToString())
End If
// Create a new Regex object.
Regex r = new Regex("abc");
// Find a single match in the string.
Match m = r.Match("123abc456");
if (m.Success)
{
// Print out the character position where a match was found.
// (Character position 3 in this case.)
Console.WriteLine("Found match at position " + m.Index);
}
MatchCollection
MatchCollection 類別代表成功的非重疊比對序列。該集合是不變的 (唯讀)，而且沒有公用建構函式。MatchCollection 的執行個體由 Regex.Matches 方法傳回。
下列範例使用 Regex 類別的 Matches 方法，將輸入字串中找到的所有相符比對填入 MatchCollection。下列範例複製集合至字串陣列 (存放各個相符比對) 和整數陣列 (指示各個相符比對的位置)。
Dim mc As MatchCollection
Dim results(20) As String
Dim matchposition(20) As Integer
' Create a new Regex object and define the regular expression.
Dim r As New Regex("abc")
' Use the Matches method to find all matches in the input string.
mc = r.Matches("123abc4abcd")
' Loop through the match collection to retrieve all
' matches and positions.
Dim i As Integer
For i = 0 To mc.Count - 1
' Add the match string to the string array.
results(i) = mc(i).Value
' Record the character position where the match was found.
matchposition(i) = mc(i).Index
Next i
MatchCollection mc;
String[] results = new String[20];
int[] matchposition = new int[20];
// Create a new Regex object and define the regular expression.
Regex r = new Regex("abc");
// Use the Matches method to find all matches in the input string.
mc = r.Matches("123abc4abcd");
// Loop through the match collection to retrieve all
// matches and positions.
for (int i = 0; i < mc.Count; i++)
{
// Add the match string to the string array.
results[i] = mc[i].Value;
// Record the character position where the match was found.
matchposition[i] = mc[i].Index;
}
GroupCollection
GroupCollection 類別代表擷取群組的集合，並傳回單一比對中擷取群組的集合。該集合是不變的 (唯讀)，而且沒有公用建構函式。GroupCollection 的執行個體會以 Match.Groups 屬性所傳回的集合傳回。
下列主控台應用程式 (Console Application) 範例尋找並印出規則運算式所擷取的群組數目。如需如何在群組集合各個成員中擷取個別擷取的範例，請參閱下個章節中的 Capture Collection 範例。
Imports System
Imports System.Text.RegularExpressions
Public Class RegexTest
Public Shared Sub RunTest()
' Define groups "abc", "ab", and "b".
Dim r As New Regex("(a(b))c")
Dim m As Match = r.Match("abdabc")
Console.WriteLine("Number of groups found = " _
& m.Groups.Count.ToString())
End Sub
Public Shared Sub Main()
RunTest()
End Sub
End Class
using System;
using System.Text.RegularExpressions;
public class RegexTest
{
public static void RunTest()
{
// Define groups "abc", "ab", and "b".
Regex r = new Regex("(a(b))c");
Match m = r.Match("abdabc");
Console.WriteLine("Number of groups found = " + m.Groups.Count);
}
public static void Main()
{
RunTest();
}
}
這個範例產生下列輸出。
Number of groups found = 3
Number of groups found = 3
CaptureCollection
CaptureCollection 類別代表擷取的子字串序列，並傳回單一擷取群組所產生的擷取集合。因為數量詞的緣故，擷取群組可以在單一比對中擷取一個以上的字串。Captures 屬性 (CaptureCollection 類別的物件) 被提供做為 Match 和 Group 類別的成員，以加速存取擷取的子字串集合。
例如，如果您使用規則運算式 ((a(b))c)+ (其中 + 數量詞會指定一或多個比對) 從字串 "abcabcabc" 擷取符合項目，對於子字串每一個比對 Group，CaptureCollection 將包含三個成員。
下列主控台應用程式範例使用規則運算式 (Abc)+，在字串 "XYZAbcAbcAbcXYZAbcAb" 中尋找一或多個符合項目。範例說明 Captures 屬性的使用，傳回擷取子字串的多個群組。
Imports System
Imports System.Text.RegularExpressions
Public Class RegexTest
Public Shared Sub RunTest()
Dim counter As Integer
Dim m As Match
Dim cc As CaptureCollection
Dim gc As GroupCollection
' Look for groupings of "Abc".
Dim r As New Regex("(Abc)+")
' Define the string to search.
m = r.Match("XYZAbcAbcAbcXYZAbcAb")
gc = m.Groups
' Print the number of groups.
Console.WriteLine("Captured groups = " & gc.Count.ToString())
' Loop through each group.
Dim i, ii As Integer
For i = 0 To gc.Count - 1
cc = gc(i).Captures
counter = cc.Count
' Print number of captures in this group.
Console.WriteLine("Captures count = " & counter.ToString())
' Loop through each capture in group.
For ii = 0 To counter - 1
' Print capture and position.
Console.WriteLine(cc(ii).ToString() _
& " Starts at character " & cc(ii).Index.ToString())
Next ii
Next i
End Sub
Public Shared Sub Main()
RunTest()
End Sub
End Class
using System;
using System.Text.RegularExpressions;
public class RegexTest
{
public static void RunTest()
{
int counter;
Match m;
CaptureCollection cc;
GroupCollection gc;
// Look for groupings of "Abc".
Regex r = new Regex("(Abc)+");
// Define the string to search.
m = r.Match("XYZAbcAbcAbcXYZAbcAb");
gc = m.Groups;
// Print the number of groups.
Console.WriteLine("Captured groups = " + gc.Count.ToString());
// Loop through each group.
for (int i=0; i < gc.Count; i++)
{
cc = gc[i].Captures;
counter = cc.Count;
// Print number of captures in this group.
Console.WriteLine("Captures count = " + counter.ToString());
// Loop through each capture in group.
for (int ii = 0; ii < counter; ii++)
{
// Print capture and position.
Console.WriteLine(cc[ii] + " Starts at character " +
cc[ii].Index);
}
}
}
public static void Main() {
RunTest();
}
}
這個範例傳回下列輸出。
Captured groups = 2
Captures count = 1
AbcAbcAbc Starts at character 3
Captures count = 3
Abc Starts at character 3
Abc Starts at character 6
Abc Starts at character 9
Captured groups = 2
Captures count = 1
AbcAbcAbc Starts at character 3
Captures count = 3
Abc Starts at character 3
Abc Starts at character 6
Abc Starts at character 9
Group
Group 類別表示單一擷取群組中的結果。因為 Group 可以在單一比對 (使用數量詞) 中擷取零個、一或多個字串，它包含 Capture 物件的集合。因為 Group 繼承自 Capture，所以可以直接存取所擷取的最後子字串 (Group 執行個體本身即等於 Captures 屬性所傳回集合的最後項目)。
Group 的執行個體會藉由編寫 Groups 屬性傳回之 GroupCollection 物件的索引來傳回。如果使用了 "(?<groupname>)" 群組建構，則索引子 (Indexer) 可以是群組編號或擷取群組的名稱。例如，在 C# 程式碼中，您可以使用 Match.Groups[groupnum] 或 Match.Groups["groupname"]，或者在 Visual Basic 程式碼中，您可以使用 Match.Groups(groupnum) 或 Match.Groups("groupname")。
下列程式碼範例使用巢狀群組建構，將子字串擷取到群組內。
Dim matchposition(20) As Integer
Dim results(20) As String
' Define substrings abc, ab, b.
Dim r As New Regex("(a(b))c")
Dim m As Match = r.Match("abdabc")
Dim i As Integer = 0
While Not (m.Groups(i).Value = "")
' Copy groups to string array.
results(i) = m.Groups(i).Value
' Record character position.
matchposition(i) = m.Groups(i).Index
i = i + 1
End While
int[] matchposition = new int[20];
String[] results = new String[20];
// Define substrings abc, ab, b.
Regex r = new Regex("(a(b))c");
Match m = r.Match("abdabc");
for (int i = 0; m.Groups[i].Value != ""; i++)
{
// Copy groups to string array.
results[i]=m.Groups[i].Value;
// Record character position.
matchposition[i] = m.Groups[i].Index;
}
這個範例傳回下列輸出。
results(0) = "abc" matchposition(0) = 3
results(1) = "ab" matchposition(1) = 3
results(2) = "b" matchposition(2) = 4
results[0] = "abc" matchposition[0] = 3
results[1] = "ab" matchposition[1] = 3
results[2] = "b" matchposition[2] = 4
下列程式碼範例使用命名的群組建構，從含有 "DATANAME:VALUE" 格式 (規則運算式以冒號 (":") 分隔) 資料的字串中擷取子字串。
Dim r As New Regex("^(?<name>\w+):(?<value>\w+)")
Dim m As Match = r.Match("Section1:119900")
Regex r = new Regex("^(?<name>\\w+):(?<value>\\w+)");
Match m = r.Match("Section1:119900");
這個規則運算式傳回下列輸出。
m.Groups("name").Value = "Section1"
m.Groups("value").Value = "119900"
m.Groups["name"].Value = "Section1"
m.Groups["value"].Value = "119900"
Capture
Capture 類別包含單一子運算式 (Subexpression) 所擷取的結果。
下列範例會對 Group 集合執行迴圈 (Loop)，從 Group 的每一個成員中擷取 Capture 集合，並分別將變數 posn 和 length 指派為原始字串中每一個找到字串的字元位置和每一個字串的長度。
Dim r As Regex
Dim m As Match
Dim cc As CaptureCollection
Dim posn, length As Integer
r = New Regex("(abc)+")
m = r.Match("bcabcabc")
Dim i, j As Integer
i = 0
While m.Groups(i).Value <> ""
' Grab the Collection for Group(i).
cc = m.Groups(i).Captures
For j = 0 To cc.Count - 1
' Position of Capture object.
posn = cc(j).Index
' Length of Capture object.
length = cc(j).Length
Next j
i += 1
End While
Regex r;
Match m;
CaptureCollection cc;
int posn, length;
r = new Regex("(abc)+");
m = r.Match("bcabcabc");
for (int i=0; m.Groups[i].Value != ""; i++)
{
// Capture the Collection for Group(i).
cc = m.Groups[i].Captures;
for (int j = 0; j < cc.Count; j++)
{
// Position of Capture object.
posn = cc[j].Index;
// Length of Capture object.
length = cc[j].Length;
}
}
請參閱
參考
System.Text.RegularExpressions