Instance variables and local variables

[diana88]

I understand that instance variables are not thread safe because they are stored on the heap. I am refactoring code in an ASP.NET single threaded application and I am trying to use instance variables more.My question is: do developers avoid using instance variables because of possible multi threading problems? (even if the app is not multi threaded now it may be in the future). I remember reading that instance variables should be used to improve design using composition and aggregation rather than association (as with local variables).Is there any criteria that helps a developer to decide when to use instance variables and when to use local variables. I have Googled this and I have looked on MSDN but I have not managed to find an answer to my specific question.