Code will be alot more organised if it's OOP developed and have more generic object and variable names than none OOP programs. Best thing to do might be to create an OOP program in something like Visual Studios to see how the code to create object is organised when you add a new object to your OOP program in comparison to non-OOP programs.
Well, if it's written in C# chances are its object oriented. Basically OOP covers anything that has a class hierarchy. I know C# supports a minimal amount of structured and functional programming, but usually this is just an 'effect' and you are actually working with objects, so you can generally assume everything written in C# is object oriented.
Most of the times, variables and the objects (of classes) have meaning ful names. What you can do is: select the variable's (or object's) name and right click on it. A popup will show up.
From here, it depends on which language you are using.
- If you are using C++, then select Go To Declaration
- If you are using C# (VB), then select Go To Definition
Once you are taken there, then you will know whether it is some variable or an object of a class.