How to close the process form class code?

I call a class form MyForm. In my class I have a if-else statements.

I want to close all process, I need a command look-like

element.close();

Example, my code:

if (_condition a_)
{
     //operations class;
}

if(_condition b_)
{
    //abort all, and close all;
}

How should I do if I am not in form? I would close all cycle by code from my class.