Good Regular Expression to Enforce Password Complexity in ASP.NET Applications

Regular expression to enforce password complexity in your applications:

^.*(?=.{10,})(?=.*\d)(?=.*[a-z])(?=.*[A-Z])(?=.*[@#$%^&+=]).*$

The regular expression enforces the following rules:

• Must be at least 10 characters
• Must contain at least one one lower case letter, one upper case letter, one digit and one special character
• Valid special characters (which are configurable) are - @#$%^&+=

Originally from Anil John's post