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.
using System; using System.Text.RegularExpressions; public class Example { public static void 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 expression \b[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 the Regex.Matches method |
|
\b |
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. |