Regular Expression Examples

This section contains code examples that illustrate the use of regular expressions in common applications.


The System.Web.RegularExpressions namespace contains a number of regular expression objects that implement predefined regular expression patterns for parsing strings from HTML, XML, and ASP.NET documents. For example, the TagRegex class identifies start tags in a string and the CommentRegex class identifies ASP.NET comments in a string.

In This Section

Example: Scanning for HREFs
Provides an example that searches an input string and prints out all the href="…" values and their locations in the string.

Example: Changing Date Formats
Provides an example that replaces dates in the form mm/dd/yy with dates in the form dd-mm-yy.

How to: Extract a Protocol and Port Number from a URL
Provides an example that extracts a protocol and port number from a string that contains a URL. For example, "" returns "http:8080".

How to: Strip Invalid Characters from a String
Provides an example that strips invalid non-alphanumeric characters from a string.

How to: Verify that Strings Are in Valid Email Format
Provides an example that verifies that a string is in valid email format.


Provides class library reference information for the .NET System.Text.RegularExpressions namespace.

.NET Regular Expressions
Provides an overview of the programming language aspect of regular expressions.

The Regular Expression Object Model
Describes the regular expression classes contained in the System.Text.RegularExpression namespace and provides examples of their use.

Details of Regular Expression Behavior
Provides information about the capabilities and behavior of .NET regular expressions.

Regular Expression Language - Quick Reference
Provides information on the set of characters, operators, and constructs that you can use to define regular expressions.