If you’re looking for a decent password strength control implementation for ASP.NET C# you could find this class I made a while ago useful enough. After all these years I’m still using it in a number of projects, from the good-old ASP.NET ASPX Forms to the new ASP.NET Core MVC applications.
The class can be used to perform basically all the required checks in a very customizable way: minimum length, maximum length, digit/numbers, special characters and so on. It features a PasswordStrength enum (and a GetPasswordStrength method) which you can use to calculate the average strength of any given password: it can be handy for general-purpose scenarios, when you don’t have to implement a given password policy. In case you have to do that, you can use the helper methods instead and combine them to suit your needs as shown in the sample implementation provided within the IsStrongPassword method – which is the one I’m still using in most cases.
The methods are quite self-explanatory, so there isn’t much more to say: if you like the class, feel free to leave a feedback in the comment section below!