Static vs non-static class members

Question

I'm new to c sharp and programming generally. I have a quick question - what is best practise with regards to static/non static variables.

I have a variable,private int x, which belongs to class y. To access this variable, i need to reference y. If x was static however, i can access this variable with no references to y.

Which is the best way to go, in a situation whereby several methods within the class y will be referencing this value ?

Hope this makes sense, and my question isn't too basic !

Many thanks

Answer 1

I completely agree with Mr Oded:

If, in all instances of the class this variable should be identical, use a static variable.

If not, use an instance variable.

Yes, adding static to a class member basically means you can access it without an instance, and only outside any instance. And yes, it becomes a global resource, or even a global variable if you will.

But I think there's at least another (heavily edited) good point to be made here...

Using static members as global vars go against OOP

This means once you set a static member you can't pass it around as an object. The more you use static as global var, the more difficult it is for unit testing / mocking classes.

There is a solution for that, Singletons. But they should never come without warnings!

At other hand, if you're sure you really need global vars, take a look at the Toolbox pattern. It's a not well known extension of Singleton pattern. It's so unknown in fact, if you google for it you won't find it with those keywords (toolbox pattern).

So plan ahead. Read more. Get to know about every option so you can decide better. Even get a book. Object Oriented Programming is more about applying concepts that will help in the long run than just making things work now.