正则表达式

VB.Net-正则表达式

.net框架提供了允许这种匹配的正则表达式引擎。模式由一个或多个字符文字，运算符或构造组成。

定义正则表达式的构造 有各种类别的字符，运算符和构造，允许您定义正则表达式。单击以下链接以查找这些结构。

• 字符转义
• 字符类
• 锚
• 分组构造
• 量词
• 反向引用结构
• 交替结构
• 替换
• 杂项结构

正则表达式类

正则表达式类用于表示一个正则表达式。

正则表达式类有以下常用方法：

有关方法和属性的完整列表，请参见Microsoft文档。

示例1 以下示例匹配以“ S”开头的单词：

Imports System.Text.RegularExpressions
Module regexProg
   Sub showMatch(ByVal text As String, ByVal expr As String)
      Console.WriteLine("The Expression: " + expr)
      Dim mc As MatchCollection = Regex.Matches(text, expr)
      Dim m As Match
      For Each m In mc
          Console.WriteLine(m)
      Next m
   End Sub
   Sub Main()
      Dim str As String = "A Thousand Splendid Suns"
      Console.WriteLine("Matching words that start with 'S': ")
      showMatch(str, "SS*")
      Console.ReadKey()
   End Sub
End Module

当上述代码被编译和执行时，它产生了以下结果：

Matching words that start with 'S':
The Expression: SS*
Splendid
Suns

例2 以下示例匹配以“ m”开头并以“ e”结尾的单词：

Imports System.Text.RegularExpressions
Module regexProg
   Sub showMatch(ByVal text As String, ByVal expr As String)
      Console.WriteLine("The Expression: " + expr)
      Dim mc As MatchCollection = Regex.Matches(text, expr)
      Dim m As Match
      For Each m In mc
          Console.WriteLine(m)
      Next m
   End Sub
   Sub Main()
      Dim str As String = "make a maze and manage to measure it"
      Console.WriteLine("Matching words that start with 'm' and ends with 'e': ")
      showMatch(str, "mS*e")
      Console.ReadKey()
   End Sub
End Module

当上述代码被编译和执行时，它产生了以下结果：

Matching words start with 'm' and ends with 'e':
The Expression: mS*e
make
maze
manage
measure

例3 此示例替换了多余的空白空间：

Imports System.Text.RegularExpressions
Module regexProg
   Sub Main()
      Dim input As String = "Hello    World   "
      Dim pattern As String = "s+"
      Dim replacement As String = " "
      Dim rgx As Regex = New Regex(pattern)
      Dim result As String = rgx.Replace(input, replacement)
      Console.WriteLine("Original String: {0}", input)
      Console.WriteLine("Replacement String: {0}", result)
      Console.ReadKey()
   End Sub
End Module

当上述代码被编译和执行时，它产生了以下结果：

Original String: Hello   World   
Replacement String: Hello World