如何防止将方法添加到类中？

Question

I'm trying to find out if there's a way to stop functions/methods from being added ( EDIT: by other developers ) to a class for the case where the object is a Model or DTO which should not contain methods (to prevent 'abuse' of the Models/DTOs by others, who may try and add 'helper' methods etc).

Is there any way to achieve this?

Answer 1

Use reflection and write a unit test that fails if a model-class has methods.

Mark all you model classes with a custom attribute. Then make a unit test that uses reflection to load a given assembly, iterate all classes in that assembly and check that classes marked with the model attribute does not have methods. This should be fairly straight forward using reflection.

Answer 2

I believe you are trying to solve a procedural issue with code where you should be using communication.

Your colleagues (i assume) are operating on the code files with 'full trust' privileges. If they break that privilege you should open a dialogue. Use the change as an opportunity to educate them on the intended design. Perhaps they are correct and you will be educated!

I suggest simply making the intended design obvious in the class name and with a comment stating the intended nature. Perhaps quote the design document(s) that informed the class.

Answer 3

You cannot hinder anyone with full write-access to your code-base to do so. The only two things you may do to avoid it are create some CodeAnalysis-rule for FXCop as mentioned by Christian.K in the comments or by writing your DTO-class so that it is undoubtly a DTO that should not have any methods by using a unambigious name for the class and if this is not enough provide some code-comments that notifies the coder to do not so.

However you may need some kind of method if using collections eg where you will need some kind of comparision if two instances of your DTO are equal, so you have to provide at least an Equals - and GetHashCode -method.

Answer 4

You don't need to use a struct to prevent additions to a class. You can use the sealed keyword

public sealed class MyDTOObject { ... }

Now, you can not inherent a class and also prevent inheritance (which is essentially what you're asking). The very fact of inheriting MyDTOObject is creating a new class which is based off of not equal to, or restricted, or defined in any way by the implementation of MyDTOObject .

You can use an abstract class, to force derived classes to implement certain methods, but not the other way around.

If you want to prevent others from deriving from your class and implementing helper methods, you must use the sealed keyword, or mark the class internal.

Answer 5

You may prevent the class being extended or inherited by marking it final that way nobody would be able to extend your class and hence not being able to add any behavior. But stop and ask yourself whether you want to do that or not, because then you'd be signing an invisible contract that everything ever required by the class is written in the class and this class needs no further addition.

To be clear, I was talking in Java context.