increase +1 everytime the methods run

Here is the hint for you: look at the context where _i is defined and its lifetime.
Try to understand one thing: local (stack) variables live only during the call. Any local variable will be initialized to same value again and again. What are other objects, except local variables? What are their lifetimes?

By the way, don't use such names, try to follow (good) Microsoft naming conventions, and never use too short names (and try to avoid too long ones).

For very advanced understanding, not related to your exact case with the named method: what I wrote about local variables is so not in all 100% cases. The exclusions come with closures: http://en.wikipedia.org/wiki/Closure_%28computer_programming%29[^].

—SA