The C# tooling is very refactor-friendly. I commonly just build the class then pull out the interface later.
C# does want to have interfaces though, and gravitates to the common interfaces - core services - composition/DI root architecture, with lots of projects in the solution to provide separation of concerns. I think it works very well generally for business software at least, but I hear plenty of grumbling about 'complexity' so it's not for everyone.
C# does want to have interfaces though, and gravitates to the common interfaces - core services - composition/DI root architecture, with lots of projects in the solution to provide separation of concerns. I think it works very well generally for business software at least, but I hear plenty of grumbling about 'complexity' so it's not for everyone.