C# 2008 Programmer's Reference

Match any character one time, if it exists
*	Match declared element multiple times, if it exists
+	Match declared element one or more times
{n}	Match declared element exactly n times
{n,}	Match declared element at least n times
{n,N}	Match declared element at least n times, but not more than N times
^	Match at the beginning of a line
$	Match at the end of a line
<	Match at the beginning of a word
>	Match at the end of a word
	Match at the beginning or end of a word
B	Match in the middle of a word
d	Shorthand for digits (0-9)
w	Shorthand for word characters (letters and digits)
s	Shorthand for whitespace

Another common search pattern is verifying a string containing a date. For example, if a string contains a date in the format 'yyyy/mm/dd', you would specify the search pattern as follows: '(19|20)dd[- /.](0[1- 9]|1[012])[- /.](0[1-9]|[12][0-9]|3[01])'. This pattern will match dates ranging from 1900-01-01 to 2099 -12-31.

string date = '2007/03/10';
Regex r = new Regex(@'(19|20)dd[- /.](0[1-9]|1[012])[- /.] (0[1-9]|[12][0-9]|3 [01])');
if (r.IsMatch(date)) {
 Console.WriteLine('Matches.');
}

You can use the following date separators with the pattern specified above:

string date = '2007/03/10'
string date = '2007-03-10'
string date = '2007 03 10'
string date = '2007.03.10'

Some commonly used search patterns are described in the following table.

Pattern	Description
[0-9]	Digits
[A-Fa-f0-9]	Hexadecimal digits
[A-Za-z0-9]	Alphanumeric characters
[A-Za-z]	Alphabetic characters
[a-z]	Lowercase letters