Question

I am I think ok at algorithmic programming, if that is the right term? I used to play with turbo pascal and 8086 assembly language back in the 1980s as a hobby. But only very small projects and I haven’t really done any programming in the 20ish years since then. So I am struggling for understanding like a drowning swimmer.

So maybe this is a very niave question or I’m just making no sense at all, but say I have an object kind of like this:

class Something : IDoer
{
    void Do(ISomethingElse x)
    {
         x.DoWhatEverYouWant(42);
    }
}

And then I do

var Thing1 = new Something();
var Thing2 = new Something();

Thing1.Do(blah);
Thing2.Do(blah);

does Thing1 = Thing2? does “new Something()” create anything? Or is it not much different different from having a static class, except I can pass it around and swap it out etc.

Is the “Do” procedure in the same location in memory for both the Thing1(blah) and Thing2(blah) objects? I mean when executing it, does it mean there are two Something.Do procedures or just one?

Answer 1

There are most definitely two different objects in memory. Each object will consume 8 bytes on the heap (at least on 32-bit systems); 4 for the syncblock and 4 for the type handle (which includes the method table). Other than the system-defined state data there is no other user-defined state data in your case.

There is a single instance of the code for the Something.Do method. The type handle pointer that each object holds is how the CLR locates the different methods for the class. So even though there are two different objects in memory they both execute the same code. Since Something.Do was declared as an instance method it will have a this pointer passed to it internally so that the code can modify the correct instance members depending on which object was invoking the method. In your case the Something class has no instance members (and thus no user-defined state) and so this is quite irrelevant, but still happens nevertheless.