Regex expression for requirements configured for the membership provider

Hello,
I'm registering new users manually (e.g. not using supplied asp.net controls).
In  AspNetSqlMembershipProvider I have following restrictions for password: passwordStrengthRegularExpression="" minRequiredPasswordLength="5" minRequiredNonalphanumericCharacters="1".
If user enters password that does not satisfy this criteria he gets error. So, I want to test password before trying to create new user. What would be Regular Expression that I can use in Regex.IsMatch() to validate these requirements?
 Thanks

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