What's the advantage of using interfaces over classes (if there are any) while using dependency-CodePudding

I'm trying to create an ASP.NET Core 5 Web API and cannot get my head around about how should i inject my dependency.

In a course that I follow the instructor uses an interface for one dependency and a class for another. So to figure out the difference among these usages, I tried to code the same dependency in a class and then in a interface.

This is the interface one:

This is the class one:

And they work exactly the same. So what is the difference? Is there any advantage using one over the other? Which one should I use in which case? Thank you so much.

CodePudding user response：

Just inject IItemRepository in any place you need and you can easily replace your implementation in future if you want only in one place (just like that: services.AddSingleton<IItemRepository, SqlServerRepository> or something like this). And, of course, you can easily write unit tests with it.