unfortunately, it's not really the same as with proper message passing/late binding like in smalltalk.

You could use C# dynamic objects to achieve late binding.

I'm not familiar with these. Are the properties and methods that dynamically add visible in the code editor?

It seems C# work by subclassing the DynamicObject class. What about dynamically extending all the other existing C# classes?

What if I subclassed a C# Queue as MyQueue and then while my days long simulation was running I wanted add an instance variable 'trackCount' to all existing MyQueue instances? In Pharo all you do is this...

Queue subclass: #MyQueue instanceVariableNames: ’trackCount’ classVariableNames: ’’ poolDictionaries: ’’ category: ’Example’

and program keeps running, this definition is updated in the editor.

of course you could also build a whole smalltalk environment in C# also, but that really is not the point.

Try a become: in C#

Gilad Bracha (co-author of the Java Language Specification) on "#become:" in Smalltalk (https://gbracha.blogspot.com.au/2009/07/miracle-of-become.ht...)

btw, see the section here on "Blub Paradox" (http://www.paulgraham.com/avg.html ) which means I'm not really competent to comment of C#'s dynamic objects.