C# callback for when a class with attribute got instantiated

Question

Is there something like a callback for when when a class Foo with a specific attribute got instantiated? A little like this pseudo code:

void OnObjectWithAttributeInstantiated(Type attributeType, object o) {
    // o is the object with the attribute
}

So i was trying to create an attribute AutoStore. Imagine the following:

Given a class Foo with that tag:

[AutoStore]
public class Foo { ... }

Then (somewhere else in the code, no matter where) you instantiate that class

Foo f = new Foo()

I now want, that this object f will be automatically added to a list of objects (e.g. in a static class or something)

If there is no such way, do you have some ideas how to do a work-around?

Edit I dont want to use a superclass which does that for purposes of clean code

Best regards Briskled

Answer 1

I don't think you can do that. Because attributes are there for you to discover at runtime. But a possible solution might be to create a factory to wrap the whole thing, like -

public class Factory
{
    public static T Instantiate<T>() where T : class
    {
        // instantiate your type
        T instant = Activator.CreateInstance<T>();

        // check if the attribute is present
        if (typeof(T).GetCustomAttribute(typeof(AutoStore), false) != null)
        {
            Container.List.Add(instant);
        }
        return instant;
    }
}

public static class Container
{
    public static List<object> List { get; set; } = new List<object>();
}

and then you can use it like -

Foo foo = Factory.Instantiate<Foo>();
foo.Bar = "Some Bar";