Character Escapes in Regular Expressions

The backslash (\) in a regular expression indicates one of the following:

• The character that follows it is a special character, as shown in the table in the following section. For example, \b is an anchor that indicates that a regular expression match should begin on a word boundary, \t represents a tab, and \x020 represents a space.

• A character that otherwise would be interpreted as an unescaped language construct should be interpreted literally. For example, a brace ({) begins the definition of a quantifier, but a backslash followed by a brace (\{) indicates that the regular expression engine should match the brace. Similarly, a single backslash marks the beginning of an escaped language construct, but two backslashes (\\) indicate that the regular expression engine should match the backslash.

Character Escapes in .NET

The following table lists the character escapes supported by regular expressions in .NET.

An Example

The following example illustrates the use of character escapes in a regular expression. It parses a string that contains the names of the world's largest cities and their populations in 2009. Each city name is separated from its population by a tab (\t) or a vertical bar (| or \u007c). Individual cities and their populations are separated from each other by a carriage return and line feed.

using System;
using System.Text.RegularExpressions;

public class Example
{
   public static void Main()
   {
      string delimited = @"\G(.+)[\t\u007c](.+)\r?\n";
      string input = "Mumbai, India|13,922,125\t\n" +
                            "Shanghai, China\t13,831,900\n" +
                            "Karachi, Pakistan|12,991,000\n" +
                            "Delhi, India\t12,259,230\n" +
                            "Istanbul, Türkiye|11,372,613\n";
      Console.WriteLine("Population of the World's Largest Cities, 2009");
      Console.WriteLine();
      Console.WriteLine("{0,-20} {1,10}", "City", "Population");
      Console.WriteLine();
      foreach (Match match in Regex.Matches(input, delimited))
         Console.WriteLine("{0,-20} {1,10}", match.Groups[1].Value,
                                            match.Groups[2].Value);
   }
}
// The example displays the following output:
//       Population of the World's Largest Cities, 2009
//
//       City                 Population
//
//       Mumbai, India        13,922,125
//       Shanghai, China      13,831,900
//       Karachi, Pakistan    12,991,000
//       Delhi, India         12,259,230
//       Istanbul, Türkiye     11,372,613

Imports System.Text.RegularExpressions

Module Example
    Public Sub Main()
        Dim delimited As String = "\G(.+)[\t\u007c](.+)\r?\n"
        Dim input As String = "Mumbai, India|13,922,125" + vbCrLf + _
                              "Shanghai, China" + vbTab + "13,831,900" + vbCrLf + _
                              "Karachi, Pakistan|12,991,000" + vbCrLf + _
                              "Delhi, India" + vbTab + "12,259,230" + vbCrLf + _
                              "Istanbul, Türkiye|11,372,613" + vbCrLf
        Console.WriteLine("Population of the World's Largest Cities, 2009")
        Console.WriteLine()
        Console.WriteLine("{0,-20} {1,10}", "City", "Population")
        Console.WriteLine()
        For Each match As Match In Regex.Matches(input, delimited)
            Console.WriteLine("{0,-20} {1,10}", match.Groups(1).Value, _
                                               match.Groups(2).Value)
        Next
    End Sub
End Module
' The example displays the following output:
'       Population of the World's Largest Cities, 2009
'       
'       City                 Population
'       
'       Mumbai, India        13,922,125
'       Shanghai, China      13,831,900
'       Karachi, Pakistan    12,991,000
'       Delhi, India         12,259,230
'       Istanbul, Türkiye     11,372,613

The regular expression \G(.+)[\t\u007c](.+)\r?\n is interpreted as shown in the following table.

See also

• Regular Expression Language - Quick Reference