C#•2y ago

❔ ✅ Stopping any additional subclassing of a class

I've got the following code:

public abstract class MyBase {}

public class MyType1 : MyBase {}
public class MyType2 : MyBase {}

public abstract class MyBase {}

public class MyType1 : MyBase {}
public class MyType2 : MyBase {}

Is there a way of stopping any other classes subclassing MyBase other than the two here? I need to be able to do these subclasses, but don't want anyone to be able to do any more.

24 Replies

Aaron•2y ago

kind of? none of them are very good though you can put all 3 types in a different assembly, with the constructors of MyBase all being internal, which means only types in that assembly can be subclasses or you can have the two derived classes be nested inside the base class, with a private constructor

Pobiega•2y ago

Yeah, access modifiers is the way to go here. but you should ask yourself why you need this and make sure this is a hard requirement, as this will break the extensbility of the system

Aaron•2y ago

actually, if you mean "anyone else" as in users of like a library you're writing, then yeah, just making the constructors of MyBase internal will do it idk how I read that differently

Hugh•2y ago

making the constructors internal sounds like it will do the job. In this case, I need all user subclasses to come from MyType1 and MyType2. However, there are some functions that will accept any subclass of MyBase And yes, I'm confident that this is a hard requirement

Pobiega•2y ago

can you clarify what you mean by "anyone else" thou? Will this be a library, or do you mean other developers in the same codebase?

Hugh•2y ago

This is in a library that is used by other applications

Pobiega•2y ago

right. then just make MyBase internal and you are good

Hugh•2y ago

"anyone else" could well include future me Perfect - thanks - appreciate it

FusedQyou•2y ago

You make them internal. You can still inherit from the same assembly, but then it's something you can control yourself

Hugh•2y ago

If I make MyBase internal, then I can't make MyType public, which I need Making the constructor internal certainly worked well though

FusedQyou•2y ago

Alternatively you make the accessibility File, assuming you're in .NET 7, and put both classes in the same file 🙃

jalepi•2y ago

Prefer composition over inheritance for better modularity and therefore better encapsulation and avoid further inheritance. Make your classes sealed, implementing a public interface for the consumers of your library.

Unknown User•2y ago

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jalepi•2y ago

Does it prevent classes being derived?

Unknown User•2y ago

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jalepi•2y ago

It works, also prevents the classes to be instantiated directly from outside the assembly. 👌

Unknown User•2y ago

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$U₹¥Δ•2y ago

mark the class with sealed keyword

Aaron•2y ago

that stops further derivation of the derived, not more derived classes of the base

Unknown User•2y ago

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Hugh•2y ago

I tried to close it a few times but the bot was down. I’ll try again now There we go

Unknown User•2y ago

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Hugh•2y ago

Oops Closing again now Thanks

Accord•2y ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ ✅ Stopping any additional subclassing of a class