title: When to use static classes and methods?
body: <p>I have a general question...when should i be using static classes or static methods?..
  I know the idea that static methods can be called without instantiating...and static classes should only be used for static methods?...but are there any performance concerns also with it...and when should they be preferred over instance methods and classes?..If someone could just briefly mention when i should opt for using them and when i should avoid them?</p>