Does the password have alphanumeric character?

Hi,
My ChangePassword method returns a boolean value indicating whether the change of password has been successful or not. When the user enters a new password, I want to check if the password length is at least 8 and there is at least one non-alphanumeric character(both these parameters specified in the web.config file). If I want to check in my code if the password entered is at least 8 characters, I would write some code like this:
if(newpassword.Length !=8)
{
//do something
}
Like the Length property, is there some property  that can check if the password contains at least one non-alphanumeric character???
Thank you!
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