I am in the process of updating a website for the third time in in 2 years, looks like this is going to happen all of the time and several websites are using the same DB. I want to use the same code for all of them and keep it easy to update in the future. So I plan on writing some interfaces and then place the business login in a service to keep things consistent across the board and add in some unit testing.
So I am looking at my current repositories and I am not sure what should be in my Interface and what should be in my Service.
For example I have an Add method - no brainer I have an Add in the interface and an add in the Service.
Then I have an AuthenticateAccountManager method that takes 3 parameters, should this be in both or just the Service and have a simple Get method in my interface (say by Username) and then do the validation against th other 2 properties in the Service.
I also have a QualifyPartner that sets a bool to true, should this just be in the Service and again have a simple Get method in my Interface, trying to keep that as small as possible?