If we're using
EntityFramework I can see why every repository should be injected in a transient lifetime, but what if we're using
Is there any problem at all?
That depends on your implemntation Dependency injection and transient documentation
Transient lifetime services (AddTransient) are created each time they're requested from the service container. This lifetime works best for lightweight, stateless services.
In my experience all repositories adhere to the above rule. Now if you have some conrner case where you have a fat state in your repository, then it might be an exception.