正则表达式（？的用法

发布时间：2020-12-14 02:18:24 所属栏目：百科来源：网络整理

导读：http://msdn.microsoft.com/en-us/library/e347654k.aspx It also allows the engine to verify that a substring exists at the end of the match without including the substring in the matched text. The following example uses positive lookahead to

http://msdn.microsoft.com/en-us/library/e347654k.aspx

It also allows the engine to verify that a substring exists at the end of the match without including the substring in the matched text. The following example uses positive lookahead to extract the words in a sentence that are not followed by punctuation symbols.

 
    C# 
   
 
    VB 
   
 
    
 
     using System;
using System.Text.RegularExpressions;

publicclass Example
{
   publicstaticvoid Main()
   {
      string pattern = @"b[A-Z]+b(?=P{P})";
      string input = "If so,what comes next?";
      foreach (Match match in Regex.Matches(input,pattern,RegexOptions.IgnoreCase))
         Console.WriteLine(match.Value);
   }
}
// The example displays the following output:
//       If
//       what
//       comes
 
    

The regular expressionb[A-Z]+b(?=P{P})is defined as shown in the following table.

Pattern	Description
b	Begin the match at a word boundary.
[A-Z]+	Match any alphabetic character one or more times. Because theRegex.Matchesmethod is called with theRegexOptions.IgnoreCaseoption,the comparison is case-insensitive.
End the match at a word boundary.
(?=P{P})	Look ahead to determine whether the next character is a punctuation symbol. If it is not,the match succeeds.

（编辑：李大同）

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正则表达式 （？的用法

正则表达式（？的用法