One of the most frustrating issues with the WPF PasswordBox is that the Password property is not a DependencyProperty. Therefore, view models can not bind to the Password property. However, this problem is solvable by creating a custom WPF control and setting up a custom Password DependencyProperty.

In https://github.com/jv813yh/UserLoginWpf/blob/master/UserLoginWpf/CreateLoginDbMVVVMDatabase.sql you have a script to create a database and insert a list of users. You can use users for login. I have only implemented Authenticate(NetworkCredential credential) and GetByName(string name) functions on database side. You can write CRUD functions, if you want. I use the ADO.NET library for working with the database, I think it is suitable for such a small project.

In https://github.com/jv813yh/UserLoginWpf/blob/master/UserLoginWpf/Repositories/RepositoryBase.cs check the connection string to see if it matches yours.