規則運算式類別
更新：2007 年 11 月
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。
' Create 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.
Console.WriteLine("Found match at position " & m.Index.ToString())
End If
' The example displays the following output:
' Found match at position 3
// 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.
Console.WriteLine("Found match at position " + m.Index);
}
// The example displays the following output:
// Found match at position 3
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 As New List(Of String)
Dim matchposition As New List(Of 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.
For i As Integer = 0 To mc.Count - 1
' Add the match string to the string array.
results.Add(mc(i).Value)
' Record the character position where the match was found.
matchposition.Add(mc(i).Index)
Next i
' List the results.
For ctr As Integer = 0 To Results.Count - 1
Console.WriteLine("'{0}' found at position {1}.", _
results(ctr), matchposition(ctr))
Next
' The example displays the following output:
' 'abc' found at position 3.
' 'abc' found at position 7.
MatchCollection mc;
List<string> results = new List<string>();
List<int> matchposition = new List<int>();
// 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.Add(mc[i].Value);
// Record the character position where the match was found.
matchposition.Add(mc[i].Index);
}
// List the results.
for(int ctr = 0; ctr <= results.Count - 1; ctr++)
Console.WriteLine("'{0}' found at position {1}.", results[ctr], matchposition[ctr]);
// The example displays the following output:
// 'abc' found at position 3.
// 'abc' found at position 7.
GroupCollection
GroupCollection 類別代表擷取的群組集合，並且會傳回單一比對中擷取的群組集合。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。
' 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)
' The example displays the following output:
' Number of groups found = 3
// 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);
// The example displays the following output:
// Number of groups found = 3
CaptureCollection
CaptureCollection 類別表示擷取的子字串序列，並且會傳回單一擷取群組完成的擷取集合。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 + 數量詞會指定一個或多個比對) 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。
下列範例使用規則運算式 (Abc)+，在字串 "XYZAbcAbcAbcXYZAbcAb" 中尋找一個或多個符合項目。範例說明 Captures 屬性的使用，傳回擷取子字串的多個群組。
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
' Display 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
' Display the number of captures in this group.
Console.WriteLine("Captures count = " & counter.ToString())
' Loop through each capture in the group.
For ii = 0 To counter - 1
' Display the capture and its position.
Console.WriteLine(cc(ii).ToString() _
& " Starts at character " & cc(ii).Index.ToString())
Next ii
Next i
' The example displays the following output:
' 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
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;
// Display 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;
// Display the number of captures in this group.
Console.WriteLine("Captures count = " + counter.ToString());
// Loop through each capture in the group.
for (int ii = 0; ii < counter; ii++)
{
// Display the capture and its position.
Console.WriteLine(cc[ii] + " Starts at character " +
cc[ii].Index);
}
}
}
// The example displays the following output:
// 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 As New List(Of Integer)
Dim results As New List(Of 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 = "")
' Add groups to string array.
results.Add(m.Groups(i).Value)
' Record character position.
matchposition.Add(m.Groups(i).Index)
i += 1
End While
' Display the capture groups.
For ctr As Integer = 0 to results.Count - 1
Console.WriteLine("{0} at position {1}", _
results(ctr), matchposition(ctr))
Next
' The example displays the following output:
' abc at position 3
' ab at position 3
' b at position 4
List<int> matchposition = new List<int>();
List<string> results = new List<string>();
// 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++)
{
// Add groups to string array.
results.Add(m.Groups[i].Value);
// Record character position.
matchposition.Add(m.Groups[i].Index);
}
// Display the capture groups.
for (int ctr = 0; ctr < results.Count; ctr++)
Console.WriteLine("{0} at position {1}",
results[ctr], matchposition[ctr]);
// The example displays the following output:
// abc at position 3
// ab at position 3
// b at position 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")
Console.WriteLine(m.Groups("name").Value)
Console.WriteLine(m.Groups("value").Value)
' The example displays the following output:
' Section1
' 119900
Regex r = new Regex("^(?<name>\\w+):(?<value>\\w+)");
Match m = r.Match("Section1:119900");
Console.WriteLine(m.Groups["name"].Value);
Console.WriteLine(m.Groups["value"].Value);
// The example displays the following output:
// Section1
// 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
Do While m.Groups(i).Value <> ""
Console.WriteLine(m.Groups(i).Value)
' Grab the Collection for Group(i).
cc = m.Groups(i).Captures
For j = 0 To cc.Count - 1
Console.WriteLine(" Capture at position {0} for {1} characters.", _
cc(j).Length, cc(j).Index)
' Position of Capture object.
posn = cc(j).Index
' Length of Capture object.
length = cc(j).Length
Next j
i += 1
Loop
' The example displays the following output:
' abcabc
' Capture at position 6 for 2 characters.
' abc
' Capture at position 3 for 2 characters.
' Capture at position 3 for 5 characters.
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++)
{
Console.WriteLine(m.Groups[i].Value);
// Capture the Collection for Group(i).
cc = m.Groups[i].Captures;
for (int j = 0; j < cc.Count; j++)
{
Console.WriteLine(" Capture at position {0} for {1} characters.",
cc[j].Length, cc[j].Index);
// Position of Capture object.
posn = cc[j].Index;
// Length of Capture object.
length = cc[j].Length;
}
}
// The example displays the following output:
// abcabc
// Capture at position 6 for 2 characters.
// abc
// Capture at position 3 for 2 characters.
// Capture at position 3 for 5 characters.
請參閱
參考
System.Text.RegularExpressions