Question

I am designing a new System and I have a lot of Interfaces that will grow over time with the system. What is the best practice to name this interfaces

ISomethingV01 ISomethingV02 etc 

and I do this

public interface ISomething{       void method(); } 

then I have to add method 2 so now what I do?

public interface ISomethingV2:ISomething{       void method2(); } 

or same other way?

Answer 1

Ideally, you shouldn’t be changing your interfaces very often (if at all). If you do need to change an interface, you should reconsider its purpose and see if the original name still applies to it.

If you still feel that the interfaces will change, and the interfaces changes are small (adding items) and you have control of the whole code base, then you should just modify the interface and fix all the compilation errors.

If your change is a change in how the interface is to be used, then you need to create a separate interface (most likely with a different name) to support that alternative usage pattern.

Even if you end up creating ISomething, ISomething2 and ISomething3, the consumers of your interfaces will have a hard time figuring out what the differences are between the interfaces. When should they use ISomething2 and when should they use ISomething3? Then you have to go about the process of obsoleting ISomething and ISomething2.