ABSTRACT
Functional programming is older than computers. It came basically from mathematical logic (lambda calculus). One of the most significant things that help the reader understand a piece of code better is to know where the source of change is. The calculator will evaluate a function composed of variables passed as parameters and expressions that form the body of the function. Delegates might be acknowledged as a definition of function prototypes where the method signature is defined. There are certain rules applied for using the variable scope in a lambda expression, like variables that are initiated within a lambda expression are not meant to be visible in an outer method. LINQ is also great to run checks for the existence of objects in a collection that match given conditions.
