Question

This might be a stupid question but I’ll ask anyway,

I was reading “OOP Demystified: A Self-Teaching Guide by Jim Keogh and Mario Giannini” chapter 11 which covers interfaces. The examples in this book are C++.

I noticed that C++ uses ISerializable to make a class serializable which you would implement where as in C# you just attribute the class with the [Serializable] attribute.

What is the key difference here? Is it that with an interface you must provide the implementation where as if you attribute something the compiler will work out the implementation for you?

I guess that with the [Serializable] attribute the .Net framework uses reflection to make the serialized object from the actual object.

That said is it possible in that case to have an [Disposable] attribute or using my theory above the framework wont know how to actually dispose of an object hence you have to do it yourself?

Would be grateful for a clarification.

Answer 1

A long time ago in a galaxy far, far away… There were no Attributes or compiler support for class metadata, so the developers tried to implement their own. One of the methods our ancestors worked out were to declare Marker Interfaces .

So, to answer your question: custom attributes are an “evolution” of marker interfaces. You can use both. But note that, if you want to enforce that your object implement specific methods, you are using an interface, plain and simple. That’s how IDisposable works, it forces you to implement a method named Dispose(). [Serializable] (and probably ISerializable on your C++ example) does not force you to implement anything, as the runtime will just read that declaration and do its task (i.e., serialize the object).

Note that C# also have a ISerializable interface… It is meant to let you write your custom serialization code, which will then be called by the runtime. Note that it is NOT a marker interface nor replacement for the [Serializable] attribute, as you still need to mark your class with the attribute for the serialization to work.